go: Bump Go's minimum version to v1.22

For #6323 (closed)

Go v1.23 was released. We added some more jobs that run the test suite on this version. This MR bumps the minimum Golang version to v1.22 from v1.21.

Both Omnibus and CNG are using Go 1.22 now:

• https://gitlab.com/gitlab-org/build/CNG/-/blob/master/ci_files/variables.yml#L31
• https://gitlab.com/gitlab-org/gitlab-omnibus-builder/-/blob/master/docker/VERSIONS#L6

We have used 1.22 for more than 3 Gitlab versions now. From distribution doc, it's okay to get rid of v1.21.

We also removed the support for that version in Workhorse ( gitlab!162822 (diffs)).