Revert "Add skill approval event/response (#12633)" (#12811)

This reverts commit https://github.com/openai/codex/pull/12633. We no
longer need this PR, because we favor sending normal exec command
approval server request with `additional_permissions` of skill
permissions instead

codex-rs/core/src/features.rs

@@ -133,8 +133,6 @@ pub enum Feature {
     SkillMcpDependencyInstall,
     /// Prompt for missing skill env var dependencies.
     SkillEnvVarDependencyPrompt,
-    /// Emit skill approval test prompts/events.
-    SkillApproval,
     /// Steer feature flag - when enabled, Enter submits immediately instead of queuing.
     /// Kept for config backward compatibility; behavior is always steer-enabled.
     Steer,
@@ -630,12 +628,6 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::UnderDevelopment,
         default_enabled: false,
     },
-    FeatureSpec {
-        id: Feature::SkillApproval,
-        key: "skill_approval",
-        stage: Stage::UnderDevelopment,
-        default_enabled: false,
-    },
     FeatureSpec {
         id: Feature::Steer,
         key: "steer",