Merge branch '500240-fix-users-solo_owned_organizations' into 'master'

Fix `Users#solo_owned_organizations` returning incorrect results when user owns multiple organizations

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/170244



Merged-by: Michał Zając <mzajac@gitlab.com>
Approved-by: Hercules Merscher <hmerscher@gitlab.com>
Approved-by: Alex Pooley <apooley@gitlab.com>
Approved-by: Michał Wielich <mwielich@gitlab.com>
Approved-by: Michał Zając <mzajac@gitlab.com>
Reviewed-by: Michał Wielich <mwielich@gitlab.com>
Co-authored-by: Shane Maglangit <smaglangit@gitlab.com>