Don't delete LfsObjectsProject when forking

When an existing project becomes a fork of another project, we
previously delete the LfsObjectsProject records of that fork.

Since we're now making each fork to have its own records, we
shouldn't delete records in that case anymore.

app/services/projects/fork_service.rb

@@ -26,17 +26,7 @@ module Projects
 
       build_fork_network_member(fork_to_project)
 
-      if link_fork_network(fork_to_project)
-        # A forked project stores its LFS objects in the `forked_from_project`.
-        # So the LFS objects become inaccessible, and therefore delete them from
-        # the database so they'll get cleaned up.
-        #
-        # TODO: refactor this to get the correct lfs objects when implementing
-        #       https://gitlab.com/gitlab-org/gitlab-foss/issues/39769
-        fork_to_project.lfs_objects_projects.delete_all
-
-        fork_to_project
-      end
+      fork_to_project if link_fork_network(fork_to_project)
     end
 
     def fork_new_project

doc/api/projects.md

@@ -2000,11 +2000,6 @@ Allows modification of the forked relationship between existing projects. Availa
 
 ### Create a forked from/to relation between existing projects
 
-CAUTION: **Warning:**
-This will destroy the LFS objects stored in the fork.
-So to retain the LFS objects, make sure you've pulled them **before** creating the fork relation,
-and push them again **after** creating the fork relation.
-
 ```
 POST /projects/:id/fork/:forked_from_id
 ```

spec/services/projects/fork_service_spec.rb

@@ -375,14 +375,6 @@ describe Projects::ForkService do
         expect(fork_from_project.forks_count).to eq(1)
       end
 
-      it 'leaves no LFS objects dangling' do
-        create(:lfs_objects_project, project: fork_to_project)
-
-        expect { subject.execute(fork_to_project) }
-          .to change { fork_to_project.lfs_objects_projects.count }
-          .to(0)
-      end
-
       context 'if the fork is not allowed' do
         let(:fork_from_project) { create(:project, :private) }