Merge branch 'docs-jl-commit-signing-ui-link' into 'master'

Linking UI signing to signed commit section

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/145599



Merged-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Approved-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Co-authored-by: Jessie Lee <jlee@gitlab.com>