Use pull request pipelinerun to trigger konflux builds.

Using the on push pipelinerun has an undesired side effect of releasing
all the renovate builds before merging them into the main branch.

Use the "on pull request" pipelinerun in an attempt to avoid this.

Signed-off-by: Miguel Martín <mmartinv@redhat.com>

.tekton/fedora-bootc-rawhide-minimal-plus-push.yaml

@@ -8,10 +8,8 @@ metadata:
     pipelinesascode.tekton.dev/cancel-in-progress: "false"
     pipelinesascode.tekton.dev/max-keep-runs: "3"
     pipelinesascode.tekton.dev/on-cel-expression: |
-      event == "push" &&
       (
-        target_branch.matches("renovate/.*") ||
-        target_branch == "main"
+        (event == "push" && target_branch == "main")
       ) && (
         ".tekton/fedora-bootc-rawhide-minimal-plus-push.yaml".pathChanged() ||
         "Containerfile".pathChanged() ||