CI: update Tekton pipelines

- Pull pipelines use odh-pr tag
- Push pipelines use odh-stable tag
- Target branch: main

Author: github-actions[bot]

.tekton/trainer-pull-request.yaml

@@ -9,8 +9,8 @@ metadata:
     build.appstudio.redhat.com/pull_request_number: '{{pull_request_number}}'
     pipelinesascode.tekton.dev/cancel-in-progress: "false"
     pipelinesascode.tekton.dev/max-keep-runs: "3"
-    pipelinesascode.tekton.dev/on-cel-expression: event == "pull_request" && target_branch
-      == "stable"
+    pipelinesascode.tekton.dev/on-cel-expression: event == "pull_request" && (target_branch
+      == "main" || target_branch == "stable")
   creationTimestamp: null
   labels:
     appstudio.openshift.io/application: opendatahub-builds