Merge branch 'renovate-workhorse/golang-1.x' into 'master'

Update dependency golang to v1.21.6

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/143886



Merged-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Approved-by: Ash McKenzie <amckenzie@gitlab.com>
Approved-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Co-authored-by: GitLab Renovate Bot <gitlab-bot@gitlab.com>

workhorse/.tool-versions

-golang 1.21.5
+golang 1.21.6