call: Add test-support feature for livekit_client_macos (#21748)

This PR updates the `call` crate to include the `test-support` feature
for `livekit_client_macos` when `call` is used with `test-support`.

This fixes running `cargo test -p copilot` and `cargo test -p editor`
(and perhaps some other crates).

Release Notes:

- N/A

crates/call/Cargo.toml

@@ -18,6 +18,7 @@ test-support = [
     "collections/test-support",
     "gpui/test-support",
     "livekit_client/test-support",
+    "livekit_client_macos/test-support",
     "project/test-support",
     "util/test-support"
 ]