Remove api_v3_commits_skip_diff_files feature flag

config/feature_flags/development/api_v3_commits_skip_diff_files.yml

----
-name: api_v3_commits_skip_diff_files
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/67647
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/344617
-milestone: '14.5'
-type: development
-group: group::integrations
-default_enabled: true

lib/api/v3/github.rb

@@ -101,8 +101,6 @@ module API
         # of time after a Gitaly timeout, to mitigate frequent Gitaly timeouts
         # for some Commit diffs.
         def diff_files(commit)
-          return commit.diffs.diff_files unless Feature.enabled?(:api_v3_commits_skip_diff_files, commit.project, default_enabled: :yaml)
-
           cache_key = [
             GITALY_TIMEOUT_CACHE_KEY,
             commit.project.id,

spec/requests/api/v3/github_spec.rb

@@ -567,18 +567,6 @@ RSpec.describe API::V3::Github do
           expect(response_diff_files(response)).to be_blank
         end
 
-        it 'does not handle the error when feature flag is disabled', :aggregate_failures do
-          stub_feature_flags(api_v3_commits_skip_diff_files: false)
-
-          allow(Gitlab::GitalyClient).to receive(:call)
-            .with(*commit_diff_args)
-            .and_raise(GRPC::DeadlineExceeded)
-
-          call_api
-
-          expect(response).to have_gitlab_http_status(:error)
-        end
-
         it 'only calls Gitaly once for all attempts within a period of time', :aggregate_failures do
           expect(Gitlab::GitalyClient).to receive(:call)
             .with(*commit_diff_args)