Merge branch 'bl-clarify-SAML-membership-and-codeowners' into 'master'

Explain incompatibility between Code Owners and Global SAML memberships lock

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/175999



Merged-by: Brendan Lynch <blynch@gitlab.com>
Approved-by: Joe Woodward <jwoodward@gitlab.com>
Reviewed-by: Joe Woodward <jwoodward@gitlab.com>