chore: don't run triage action on PR source (#19731)

currently failing on the source run.

This is unnecessary to have anyway

(goofed up and got source and target mixed up initially on the first commit 🙈)

----

### All Submissions:

* [ ] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [ ] Did you use `cdk-integ` to deploy the infrastructure and generate the snapshot (i.e. `cdk-integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

.github/workflows/issue-label-assign.yml

@@ -2,8 +2,6 @@ name: "Set Issue Label and Assignee"
 on:
  issues:
     types: [opened, edited]
- pull_request:
-    types: [opened]
  pull_request_target:
     types: [opened]