.github: apply timeout to pytest regress (#7142)

These test runs usually take 20-30 minutes. if something hangs, we see
actions proceeding for several hours: it's more convenient to have them
time out sooner so that we notice that something has hung faster.

.github/workflows/build_and_test.yml

@@ -461,6 +461,7 @@ jobs:
 
       - name: Pytest regression tests
         uses: ./.github/actions/run-python-test-set
+        timeout-minutes: 60
         with:
           build_type: ${{ matrix.build_type }}
           test_selection: regress