Temporarily disable PHP 8.1 tests

Most of the failures are just noise related to argument nullability
deprecations that we can clean up, for now, I'd like to see green
tests.

Author: NattyNarwhal

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
   ubuntu:
     strategy:
       matrix:
-          version: ['7.3', '7.4', '8.0', '8.1']
+          version: ['7.3', '7.4', '8.0']
     runs-on: ubuntu-latest
     steps:
       - name: Checkout