chore(config) rm experimental_use_freeform_apply_patch (#22565)

## Summary
Get rid of the `experimental_use_freeform_apply_patch` config option,
since it is now encoded in model config. No deprecation message since it
has been experimental this entire time.

## Testing
- [x] Updated unit tests

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/features/src/lib.rs

@@ -286,7 +286,6 @@ pub struct Features {
 
 #[derive(Debug, Clone, Default)]
 pub struct FeatureOverrides {
-    pub include_apply_patch_tool: Option<bool>,
     pub web_search_request: Option<bool>,
 }
 
@@ -294,17 +293,11 @@ pub struct FeatureOverrides {
 pub struct FeatureConfigSource<'a> {
     pub features: Option<&'a FeaturesToml>,
     pub include_apply_patch_tool: Option<bool>,
-    pub experimental_use_freeform_apply_patch: Option<bool>,
     pub experimental_use_unified_exec_tool: Option<bool>,
 }
 
 impl FeatureOverrides {
     fn apply(self, features: &mut Features) {
-        LegacyFeatureToggles {
-            include_apply_patch_tool: self.include_apply_patch_tool,
-            ..Default::default()
-        }
-        .apply(features);
         if let Some(enabled) = self.web_search_request {
             if enabled {
                 features.enable(Feature::WebSearchRequest);
@@ -470,7 +463,6 @@ impl Features {
         for source in [base, profile] {
             LegacyFeatureToggles {
                 include_apply_patch_tool: source.include_apply_patch_tool,
-                experimental_use_freeform_apply_patch: source.experimental_use_freeform_apply_patch,
                 experimental_use_unified_exec_tool: source.experimental_use_unified_exec_tool,
             }
             .apply(&mut features);