Update pa11y_test.yaml

[YvonneKallberg]

No description provided.

[YvonneKallberg]

Is it as simple as replacing

  workflow_dispatch:
  schedule:
    - cron: '25 8,12 * * *'

with

  pull_request:
    push:
      branches:
        - main

If so, it's done, but how can one test?

[YvonneKallberg]

Hmm, check unsuccessful (plan page anchor wrong), due to the check being done on the site (which hasn't been redeployed after plan page was changed). Hence, what is the point of running pa11y at all, weekly or on PRs, if it only runs on deployed page?