copilot: Switch to official @github/copilot-language-server (#27401)

This PR updates Copilot to use the official
[`@github/copilot-language-server`](https://github.com/github/copilot-language-server-release).

It's [available on
npm](https://www.npmjs.com/package/@github/copilot-language-server), so
we're installing it from there.

I tested it out locally and it seemed to be working as expected.

Release Notes:

- Updated Copilot to use the official
[`@github/copilot-language-server`](https://github.com/github/copilot-language-server-release).

crates/copilot/Cargo.toml

@@ -26,8 +26,6 @@ test-support = [
 
 [dependencies]
 anyhow.workspace = true
-async-compression.workspace = true
-async-tar.workspace = true
 chrono.workspace = true
 client.workspace = true
 collections.workspace = true
@@ -49,7 +47,6 @@ schemars = { workspace = true, optional = true }
 serde.workspace = true
 serde_json.workspace = true
 settings.workspace = true
-smol.workspace = true
 strum.workspace = true
 task.workspace = true
 ui.workspace = true