Ensure CI can run on forked repo PRs

Hardcode the runner in the workflow directly instead of GH project
config as it’s not available to the forked repositories otherwise when
submitting PRs: https://github.com/orgs/community/discussions/44322.
Workflow environment variables are not accessible on runs-on either.

.github/workflows/qa.yaml

@@ -16,7 +16,10 @@ env:
 jobs:
   sanity:
     name: Code sanity
-    runs-on: ${{ vars.RUNNER }}
+    # Put the runner here instead of GH project config as it’s not available to the forked repositories
+    # otherwise when submitting PRs: https://github.com/orgs/community/discussions/44322.
+    # workflow environements don’t work either.
+    runs-on: ubuntu-24.04
     steps:
       - name: Install dependencies
         run: |
@@ -43,7 +46,7 @@ jobs:
 
   tests:
     name: Tests
-    runs-on: ${{ vars.RUNNER }}
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5