This PR fixes a panic that would occur when loading an extension using
v0.2.0 of the extension API after #25357 landed:
```
Thread "<unnamed>" panicked with "called `Result::unwrap()` on an `Err` value: map entry `zed:extension/github` defined twice" at crates/extension_host/src/wasm_host/wit.rs:38:31
10a6cd00e7/src/crates/extension_host/src/wasm_host/wit.rs (L38) (may not be uploaded, line may be incorrect if files modified)
0: backtrace::backtrace::libunwind::trace
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/backtrace-0.3.74/src/backtrace/libunwind.rs:116:5
backtrace::backtrace::trace_unsynchronized
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/backtrace-0.3.74/src/backtrace/mod.rs:66:5
1: backtrace::backtrace::trace
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/backtrace-0.3.74/src/backtrace/mod.rs:53:14
2: backtrace::capture::Backtrace::create
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/backtrace-0.3.74/src/capture.rs:292:9
3: backtrace::capture::Backtrace::new
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/backtrace-0.3.74/src/capture.rs:257:22
4: zed::reliability::init_panic_hook::{{closure}}
at /Users/maxdeviant/projects/zed/crates/zed/src/reliability.rs:56:29
5: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2084:9
std::panicking::rust_panic_with_hook
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:808:13
6: std::panicking::begin_panic_handler::{{closure}}
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:674:13
7: std::sys::backtrace::__rust_end_short_backtrace
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:168:18
8: rust_begin_unwind
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:665:5
9: core::panicking::panic_fmt
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/panicking.rs:74:14
10: core::result::unwrap_failed
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/result.rs:1679:5
11: core::result::Result<T,E>::unwrap
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/result.rs:1102:23
extension_host::wasm_host::wit::new_linker
at /Users/maxdeviant/projects/zed/crates/extension_host/src/wasm_host/wit.rs:38:5
12: extension_host::wasm_host::wit::since_v0_2_0::linker::{{closure}}
at /Users/maxdeviant/projects/zed/crates/extension_host/src/wasm_host/wit/since_v0_2_0.rs:43:9
13: std::sync::once_lock::OnceLock<T>::get_or_init::{{closure}}
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once_lock.rs:276:50
14: std::sync::once_lock::OnceLock<T>::initialize::{{closure}}
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once_lock.rs:483:19
15: std::sync::once::Once::call_once_force::{{closure}}
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once.rs:217:40
16: std::sys::sync::once::queue::Once::call
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/sync/once/queue.rs:183:21
17: std::sync::once::Once::call_once_force
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once.rs:217:9
18: std::sync::once_lock::OnceLock<T>::initialize
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once_lock.rs:482:9
19: std::sync::once_lock::OnceLock<T>::get_or_try_init
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once_lock.rs:364:9
20: std::sync::once_lock::OnceLock<T>::get_or_init
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sync/once_lock.rs:276:15
21: extension_host::wasm_host::wit::since_v0_2_0::linker
at /Users/maxdeviant/projects/zed/crates/extension_host/src/wasm_host/wit/since_v0_2_0.rs:42:5
22: extension_host::wasm_host::wit::Extension::instantiate_async::{{closure}}
at /Users/maxdeviant/projects/zed/crates/extension_host/src/wasm_host/wit.rs:122:17
23: extension_host::wasm_host::WasmHost::load_extension::{{closure}}
at /Users/maxdeviant/projects/zed/crates/extension_host/src/wasm_host.rs:385:14
24: <core::pin::Pin<P> as core::future::future::Future>::poll
at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/future/future.rs:123:9
25: async_task::raw::RawTask<F,T,S,M>::run
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/async-task-4.7.1/src/raw.rs:557:17
26: async_task::runnable::Runnable<M>::run
at /Users/maxdeviant/.cargo/registry/src/index.crates.io-6f17d22bba15001f/async-task-4.7.1/src/runnable.rs:781:18
27: gpui::platform::mac::dispatcher::trampoline
at /Users/maxdeviant/projects/zed/crates/gpui/src/platform/mac/dispatcher.rs:106:5
28: <unknown>
29: <unknown>
30: <unknown>
31: _pthread_mach_thread_np
```
We don't need the added `add_to_linker` calls anymore.
Release Notes:
- N/A
a9e753fc07