Use AwardEmoji constants for thumbs (ruby)

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/169473



Merged-by: Brett Walker <bwalker@gitlab.com>
Approved-by: Adie (she/her) <avpfestin@gitlab.com>
Approved-by: Rodrigo Tomonari <rtomonari@gitlab.com>
Approved-by: Jon Jenkins <jjenkins@gitlab.com>