Remove the commit count from the commits API

This removes the feature flag that was removing the commit count from
the API.

The commit count was adding an extra Gitaly call to populate the total
headers.

changelogs/unreleased/bvl-remove-ff-commits-count.yml

+---
+title: Remove the commit count from the commits API
+merge_request: 44934
+author:
+type: performance

config/feature_flags/development/api_commits_without_count.yml

----
-name: api_commits_without_count
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/43159
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/254994
-type: development
-group: team::Scalability
-default_enabled: false

lib/api/commits.rb

@@ -64,7 +64,6 @@ module API
 
         serializer = with_stats ? Entities::CommitWithStats : Entities::Commit
 
-        if Feature.enabled?(:api_commits_without_count, user_project)
         # This tells kaminari that there is 1 more commit after the one we've
         # loaded, meaning there will be a next page, if the currently loaded set
         # of commits is equal to the requested page size.
@@ -72,19 +71,6 @@ module API
         paginated_commits = Kaminari.paginate_array(commits, total_count: commit_count)
 
         present paginate(paginated_commits, exclude_total_headers: true), with: serializer
-        else
-          commit_count =
-            if all || path || before || after || first_parent
-              user_project.repository.count_commits(ref: ref, path: path, before: before, after: after, all: all, first_parent: first_parent)
-            else
-              # Cacheable commit count.
-              user_project.repository.commit_count_for_ref(ref)
-            end
-
-          paginated_commits = Kaminari.paginate_array(commits, total_count: commit_count)
-
-          present paginate(paginated_commits), with: serializer
-        end
       end
 
       desc 'Commit multiple file changes as one commit' do

spec/requests/api/commits_spec.rb

@@ -40,17 +40,6 @@ RSpec.describe API::Commits do
 
         expect(response).to include_limited_pagination_headers
       end
-
-      it 'includes the total headers when the count is not disabled' do
-        stub_feature_flags(api_commits_without_count: false)
-        commit_count = project.repository.count_commits(ref: 'master').to_s
-
-        get api(route, current_user)
-
-        expect(response).to include_pagination_headers
-        expect(response.headers['X-Total']).to eq(commit_count)
-        expect(response.headers['X-Page']).to eql('1')
-      end
     end
 
     context 'when unauthenticated', 'and project is public' do