Merge branch 'replace-shared-runners-with-instance-runners-2' into 'master'

Replace the term shared runners with instance runners

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/171128



Merged-by: Suzanne Selhorn <sselhorn@gitlab.com>
Approved-by: Gabriel Engel <gengel@gitlab.com>
Co-authored-by: Roshni Sarangadharan <rsarangadharan@gitlab.com>