packit: Enable use_target_repo_for_fmf_url option

Currently this is picked up from the main branch of the fork which is
suboptimal. The packit folks implemented this new option for us which
should fix the problem.

.packit.yml

@@ -38,5 +38,6 @@ jobs:
   trigger: pull_request
   fmf_path: test/fmf
   tmt_plan: ci
+  use_target_repo_for_fmf_url: true
   targets:
   - fedora-rawhide-x86_64