Add backend patterns to jest rules

What does this MR do and why?

Add backend patterns to the jest and jest:minimal rules that were missed in https://gitlab.com/gitlab-org/gitlab/-/merge_requests.

For now, backend changes should still trigger full jest jobs because of the dependency on fixtures.

The plan to link fixtures changes to frontend tests would in the issue #339343 (closed).

Without this link, the jest minimal jobs on backend changes would not run any tests.