Merge branch '143216_remove_unused_code' into 'master'

Remove unused code from DiffTree

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144604



Merged-by: Marc Shaw <mshaw@gitlab.com>
Approved-by: Gavin Hinfey <ghinfey@gitlab.com>
Approved-by: Marc Shaw <mshaw@gitlab.com>
Co-authored-by: Vasilii Iakliushin <viakliushin@gitlab.com>