Fix spec/features/instance_statistics/cohorts_spec.rb
Fix spec/features/instance_statistics/cohorts_spec.rb

If one spec disables the usage ping in the in-memory application settings
(e.g. spec/features/usage_stats_consent_spec.rb), then this spec will
fail. To work around this problem, we enable the usage ping explicitly
in the setup phase.

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7290

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