Pin used actions to commits; update them to the latest, including actions/checkout (which was v1 and was deprecated 2025-02-01)

Author: jkachel

.github/workflows/ci.yml

@@ -5,18 +5,18 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
       - name: Set up JS requirements
         run: npm install
 
       - name: Set up Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@42375524e23c412d93fb67b49958b491fce71c38 # v5.4.0
         with:
           python-version: "3.9"
 
       - id: cache
-        uses: actions/cache@v1
+        uses: actions/cache@d4323d4df104b026a6aa633fdb11d772146be0bf # v4.2.2
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt', '**/test_requirements.txt') }}