Use the ListCommits RPC, not CommitsBetween, when processing git push

The latter is obsoleted by the former, and is more amenable to commit
limiting, which will come in a later commit.

Changelog: performance

config/feature_flags/development/between_uses_list_commits.yml

----
-name: between_uses_list_commits
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/67591
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/337960
-milestone: '14.2'
-type: development
-group: group::source code
-default_enabled: false

lib/gitlab/git/commit.rb

@@ -116,13 +116,9 @@ module Gitlab
           return [] if Gitlab::Git.blank_ref?(base) || Gitlab::Git.blank_ref?(head)
 
           wrapped_gitaly_errors do
-            if Feature.enabled?(:between_uses_list_commits, default_enabled: :yaml)
-              revisions = [head, "^#{base}"] # base..head
+            revisions = [head, "^#{base}"] # base..head
 
-              repo.gitaly_commit_client.list_commits(revisions, reverse: true)
-            else
-              repo.gitaly_commit_client.between(base, head)
-            end
+            repo.gitaly_commit_client.list_commits(revisions, reverse: true)
           end
         end
 

spec/lib/gitlab/git/commit_spec.rb

@@ -370,14 +370,6 @@ RSpec.describe Gitlab::Git::Commit, :seed_helper do
       end
 
       it { is_expected.to contain_exactly(SeedRepo::Commit::ID) }
-
-      context 'between_uses_list_commits FF disabled' do
-        before do
-          stub_feature_flags(between_uses_list_commits: false)
-        end
-
-        it { is_expected.to contain_exactly(SeedRepo::Commit::ID) }
-      end
     end
 
     describe '.shas_with_signatures' do