Configure packit to use caret notation for postrelease snapshots

This ensures the build of that specific version is considered newer than
any other regular release of it.

For rpm-software-management/ci-dnf-stack#1843

Author: kontura

.packit.yml

@@ -1,4 +1,6 @@
 specfile_path: fedora/libmodulemd.spec
+version_suffix: "^{PACKIT_PROJECT_SNAPSHOTID}"
+update_release: false
 upstream_package_name: libmodulemd
 upstream_project_url: https://github.com/fedora-modularity/libmodulemd
 downstream_package_name: libmodulemd