De-duplicate two specs in spec/services/notification_service_spec
De-duplicate two specs in spec/services/notification_service_spec

There were two specs that were testing the exact same thing as the spec
above it, but with additional expectations. So we opted to keep the
"more expectations" tests and deleted the duplicates.

We've also deleted one nested `before` block that was duplicating setup
of its parent context.

dreampet/gitlab,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,dreampet/gitlab,jirutka/gitlabhq,jirutka/gitlabhq,t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq