Move etag caching middleware after rack middleware

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127368



Merged-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Approved-by: Gregorius Marco <gmarco@gitlab.com>
Approved-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Reviewed-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Reviewed-by: Gregorius Marco <gmarco@gitlab.com>
Co-authored-by: Sylvester Chin <schin@gitlab.com>