fix: Add target ns annotation to on-tag

We missed it and this was causing all soft of issues when running the
tests, like this error:

"test/gitlab_merge_request_test.go:687", "msg":"Changing Title on MergeRequest
https://gitlab.pipelinesascode.com/pac/e2e-testing/-/merge_requests/184"}
gitlab_merge_request_test.go:697: assertion failed: len(prs.Items) is not 2
--- FAIL: TestGitlabMergeRequestOnUpdateAtAndLabelChange (33.54s)

Signed-off-by: Chmouel Boudjnah <chmouel@redhat.com>

Author: chmouel

test/testdata/failures/pipelinerun-invalid-cel.yaml

@@ -5,6 +5,7 @@ metadata:
   name: "\\ .PipelineName //"
   annotations:
     pipelinesascode.tekton.dev/on-cel-expression: event == "pull request" |
+    pipelinesascode.tekton.dev/target-namespace: "\\ .TargetNamespace //"
 spec:
   pipelineSpec:
     tasks:

test/testdata/pipelinerun-on-tag.yaml

@@ -4,6 +4,7 @@ kind: PipelineRun
 metadata:
   name: "pipelinerun-on-tag"
   annotations:
+    pipelinesascode.tekton.dev/target-namespace: "\\ .TargetNamespace //"
     pipelinesascode.tekton.dev/on-target-branch: "[\\ .TargetBranch //]"
     pipelinesascode.tekton.dev/on-event: "[push]"
 spec: