Remove source_project_id from basic search for merge requests

lib/gitlab/search_results.rb

@@ -188,7 +188,7 @@ module Gitlab
       merge_requests = MergeRequestsFinder.new(current_user, issuable_params).execute
 
       unless default_project_filter
-        merge_requests = merge_requests.in_projects(project_ids_relation)
+        merge_requests = merge_requests.of_projects(project_ids_relation)
       end
 
       apply_sort(merge_requests, scope: 'merge_requests')

spec/lib/gitlab/search_results_spec.rb

@@ -144,13 +144,13 @@ RSpec.describe Gitlab::SearchResults do
       end
     end
 
-    it 'includes merge requests from source and target projects' do
+    it 'does not include merge requests from source projects' do
       forked_project = fork_project(project, user)
       merge_request_2 = create(:merge_request, target_project: project, source_project: forked_project, title: 'foo')
 
       results = described_class.new(user, 'foo', Project.where(id: forked_project.id))
 
-      expect(results.objects('merge_requests')).to include merge_request_2
+      expect(results.objects('merge_requests')).not_to include merge_request_2
     end
 
     describe '#merge_requests' do