Delete pull-requests-opened.yml (#11890)

This action doesn't work as expected given that public forks don't have access to the token.

.github/workflows/pull-requests-opened.yml

@@ -1,16 +0,0 @@
-on:
-  pull_request:
-    types:
-      - opened
-permissions:
-  contents: read
-
-jobs:
-  add-to-project:
-    name: Add pull-requests to request queue
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/add-to-project@main
-        with:
-          project-url: https://github.com/orgs/hashicorp/projects/105
-          github-token: ${{ secrets.PACKER_PROJ_BOARD_TOKEN }}