Bump sentry-raven gem to 2.7.4
Bump sentry-raven gem to 2.7.4

Contains only minor fixes from 2.7.2:
https://github.com/getsentry/raven-ruby/releases

mmkassem/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,iiet/iiet-git,iiet/iiet-git,axilleas/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,iiet/iiet-git,stoplightio/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq