Remove copilot and show_copilot_suggestions setting aliases (#13167)

This PR removes the Copilot-specific aliases for the
`inline_completions` and `show_inline_completions` settings.

While these aliases were added to maintain backward-compatibility, the
aliasing behavior here can lead to a confusing experience when both keys
end up in the `settings.json`.

Release Notes:

- Breaking Change: Removed the `copilot` alias for the
`inline_completions` setting. If you have settings under `copilot` they
should get moved to `inline_completions`.
- Breaking Change: Removed the `show_copilot_suggestions` alias for the
`show_inline_completions` setting.

crates/language/src/language_settings.rs

@@ -194,7 +194,7 @@ pub struct AllLanguageSettingsContent {
     #[serde(default)]
     pub features: Option<FeaturesContent>,
     /// The inline completion settings.
-    #[serde(default, alias = "copilot")]
+    #[serde(default)]
     pub inline_completions: Option<InlineCompletionSettingsContent>,
     /// The default language settings.
     #[serde(flatten)]
@@ -297,7 +297,7 @@ pub struct LanguageSettingsContent {
     /// or manually by triggering `editor::ShowInlineCompletion` (false).
     ///
     /// Default: true
-    #[serde(default, alias = "show_copilot_suggestions")]
+    #[serde(default)]
     pub show_inline_completions: Option<bool>,
     /// Whether to show tabs and spaces in the editor.
     #[serde(default)]