Add comments about removing some methods later

These methods won't be necessary once all the `LfsObjectsProject`
are backfilled for forks.

app/models/project.rb

@@ -1357,6 +1357,10 @@ class Project < ApplicationRecord
     forked_from_project || fork_network&.root_project
   end
 
+  # TODO:  Remove this method once all LfsObjectsProject records are backfilled
+  # for forks.
+  #
+  # See https://gitlab.com/gitlab-org/gitlab/issues/122002 for more info.
   def lfs_storage_project
     @lfs_storage_project ||= begin
       result = self

app/services/projects/unlink_fork_service.rb

@@ -52,6 +52,10 @@ module Projects
       Projects::ForksCountService.new(project).refresh_cache
     end
 
+    # TODO: Remove this method once all LfsObjectsProject records are backfilled
+    # for forks.
+    #
+    # See https://gitlab.com/gitlab-org/gitlab/issues/122002 for more info.
     def save_lfs_objects
       return unless @project.forked?