Merge branch '503095-migrate-gl-text-gray-900-gl-text-default' into 'master'

Replace gl-text-gray-900 with gl-text-default

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172960



Merged-by: Ezekiel Kigbo <3397881-ekigbo@users.noreply.gitlab.com>
Approved-by: Dan MH <dmizzi-harris@gitlab.com>
Approved-by: Lukas Wanko <lwanko@gitlab.com>
Approved-by: Eduardo Sanz García <esanz-garcia@gitlab.com>
Reviewed-by: Ezekiel Kigbo <3397881-ekigbo@users.noreply.gitlab.com>
Reviewed-by: Justin Ho Tuan Duong <hduong@gitlab.com>
Reviewed-by: Dan MH <dmizzi-harris@gitlab.com>
Reviewed-by: Scott de Jonge <sdejonge@gitlab.com>
Reviewed-by: Lukas Wanko <lwanko@gitlab.com>
Co-authored-by: sdejonge <sdejonge@gitlab.com>