FIX: Pending post deletion by creator (#23130)

`ReviewableQueuedPost` got refactored a while back to use the more
appropriate `target_created_by` for the user of the post being queued
instead of `created_by`. The change was not extended to the `DELETE
/review/:id` endpoint leading to error responses for a user attempting
to deleting their own queued post.

This fix extends the `Reviewable` lookup implementation in
`ReviewablesController#destroy` and Guardian implementation to account
for this change.

spec/lib/guardian_spec.rb

@@ -4389,7 +4389,7 @@ RSpec.describe Guardian do
 
     context "when attempting to destroy your own reviewable" do
       it "returns true" do
-        queued_post = Fabricate(:reviewable_queued_post, created_by: user)
+        queued_post = Fabricate(:reviewable_queued_post, target_created_by: user)
         env =
           create_request_env(path: "/review/#{queued_post.id}.json").merge(
             { "REQUEST_METHOD" => "DELETE" },