Fix code actions migration (#40303)

Closes #40270

Release Notes:

- Fixed an issue with the settings migration to flatten `code_actions`
format steps where comments would cause enabled code actions to be
omitted from the migrated settings. If you were effected, restoring the
settings file backup and allowing the migration to re-run will result in
a valid settings file
- Fixed an issue where automated settings and keymap file updates would
occasionally assume 4-space indentation

crates/migrator/src/patterns.rs

@@ -10,4 +10,5 @@ pub(crate) use settings::{
     SETTINGS_ASSISTANT_PATTERN, SETTINGS_ASSISTANT_TOOLS_PATTERN,
     SETTINGS_DUPLICATED_AGENT_PATTERN, SETTINGS_EDIT_PREDICTIONS_ASSISTANT_PATTERN,
     SETTINGS_LANGUAGES_PATTERN, SETTINGS_NESTED_KEY_VALUE_PATTERN, SETTINGS_ROOT_KEY_VALUE_PATTERN,
+    migrate_language_setting,
 };