.github/workflows/ci.yaml: Resolve Python environment error for pre-commit job by running in BAPCtools container

See pre-commit/action#210,
apparently we were missing this setup action

Author: mpsijm

.github/workflows/ci.yaml

@@ -6,6 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-python@v3
       - uses: pre-commit/action@v3.0.1
 
   test: