lua: Fix broken LuaLS download on x64 (#10642)

The changes in #10437 accidentally switched 'x64' to 'x86_64' which
breaks installs on linux x64, macos x64 and windows x64. This yields the
following error:

```
[2024-04-16T12:58:01-04:00 ERROR project] failed to start language server "lua-language-server": no asset found matching "lua-language-server-3.7.4-darwin-x86_64.tar.gz"
[2024-04-16T12:58:01-04:00 ERROR project] server stderr: Some("")
```

It's trying to download: 
`lua-language-server-3.7.4-darwin-x86_64.tar.gz`
which should be
`lua-language-server-3.7.4-darwin-x64.tar.gz`

See [LuaLS release
page](https://github.com/LuaLS/lua-language-server/releases/tag/3.6.25).

CC: @maxbrunsfeld

lua.rs before ef4c70c:

c6028f6651/crates/languages/src/lua.rs (L35)

lua.rs after:

5d7148bde1/extensions/lua/src/lua.rs (L49)

Release Notes:

- N/A

extensions/lua/src/lua.rs

@@ -46,7 +46,7 @@ impl LuaExtension {
             },
             arch = match arch {
                 zed::Architecture::Aarch64 => "arm64",
-                zed::Architecture::X8664 => "x86_64",
+                zed::Architecture::X8664 => "x64",
                 zed::Architecture::X86 => return Err("unsupported platform x86".into()),
             },
         );