Merge branch 'security-do-not-process-mr-ref-for-guests-11-6' into 'security-11-6'
[11.6] Don't process MR refs for guests in the notes See merge request gitlab/gitlabhq!2782 (cherry picked from commit ee0f107791921dec7a6e3d43fe45ebef43d864be) 6e10237d Don't process MR refs for guests in the notes