Rename phpdoc-to-github-pages to phpdoc-to-github-pages.yml (#1425)

- follow up to #1418, where I named the file without the required YML suffix
- Do not run on pull requests

Author: svrnm

.github/workflows/phpdoc-to-github-pages renamed to .github/workflows/phpdoc-to-github-pages.yml

@@ -4,7 +4,6 @@ on:
   push:
     branches:
       - "main"
-  pull_request:
   workflow_dispatch:
 
 # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages