Fix configuration for Packit 1.0.0

This commit fixes the configuration for the forthcoming Packit 1.0.0.
See [our blog post](https://packit.dev/posts/packit_1_0_0_action_required) for more details.
  - Job type `build` has been changed to `copr_build`.
  - Job type `production_build` has been changed to `upstream_koji_build`.
  - Key `upstream_project_name` has been changed to `upstream_package_name`.
  - Key `synced_files` has been changed to `files_to_sync`.

Please review and merge me before January 2025 otherwise packit-service jobs will fail because of an invalid configuration.

.packit.yaml

@@ -56,7 +56,7 @@ jobs:
     trigger: release
 
   # create an srpm from upstream and submit a scratch build to koji
-  - job: production_build
+  - job: upstream_koji_build
     trigger: release
 
   # trigger a build in koji for a new dist-git commit