Revert part of "Merge branch 'update_issues_mr_counter' into 'master'

app/controllers/concerns/issuable_collections.rb

app/controllers/concerns/issues_action.rb

app/controllers/concerns/merge_requests_action.rb

app/controllers/projects/issues_controller.rb

app/controllers/projects/merge_requests_controller.rb

app/helpers/application_helper.rb

app/views/shared/issuable/_nav.html.haml

spec/features/dashboard_issues_spec.rb

spec/features/issues/filter_issues_spec.rb