[skip-ci] Packit: packages: [skopeo-fedora] for podman-next jobs

Without this change, packit will trigger duplicate jobs on podman-next
for `skopeo-fedora`, `skopeo-centos` etc, which essentially point to the
same file.

1 job triggered builds packages for all environments enabled on the
COPR, so simply `skopeo-fedora` should suffice.

Signed-off-by: Lokesh Mandvekar <lsm5@redhat.com>

.packit.yaml

@@ -63,6 +63,7 @@ jobs:
   # Run on commit to main branch
   - job: copr_build
     trigger: commit
+    packages: [skopeo-fedora]
     notifications:
       failure_comment:
         message: "podman-next COPR build failed. @containers/packit-build please check."