Fixes pagination URL on old merge request search page

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/165494



Merged-by: Kushal Pandya <kushal@gitlab.com>
Approved-by: Kerri Miller <kerrizor@kerrizor.com>
Approved-by: Kushal Pandya <kushal@gitlab.com>
Co-authored-by: Phil Hughes <me@iamphill.com>