Remove the `ForkedProjectLink` model

This removes the `ForkedProjectLink` model that has been replaced by
the `ForkNetworkMember` and `ForkNetwork` combination. All existing
relations have been adjusted to use these new models.

The `forked_project_link` table has been dropped.

The "Forks" count on the admin dashboard has been updated to count all
`ForkNetworkMember` rows and deduct the number of `ForkNetwork`
rows. This is because now the "root-project" of a fork network also
has a `ForkNetworkMember` row. This count could become inaccurate when
the root of a fork network is deleted.

1 files changed, 2 insertions, 2 deletions

diff --git a/spec/workers/namespaceless_project_destroy_worker_spec.rb b/spec/workers/namespaceless_project_destroy_worker_spec.rb
index eec110dfbfb..2f21a1321e1 100644
--- a/spec/workers/namespaceless_project_destroy_worker_spec.rb
+++ b/spec/workers/namespaceless_project_destroy_worker_spec.rb
@@ -71,10 +71,10 @@ describe NamespacelessProjectDestroyWorker do
           expect(merge_request.reload).to be_closed
         end
 
-        it 'destroys the link' do
+        it 'destroys fork network members' do
           subject.perform(project.id)
 
-          expect(parent_project.forked_project_links).to be_empty
+          expect(parent_project.forked_to_members).to be_empty
         end
       end
     end