chore(ci): Pin GitHub Actions to commit SHAs

Pin GitHub Actions references to full commit SHAs instead of version
tags to reduce supply chain risk from tag retargeting.

Update actions/checkout to v6.0.2, actions/setup-python to v6.2.0,
actions/setup-node to v6.3.0, actions/stale to v10.2.0, and
dessant/lock-threads to v6.0.0.

.github/workflows/update-translation-strings.yml

@@ -27,12 +27,12 @@ jobs:
         private-key: ${{ secrets.HOUSEKEEPING_SECRET_KEY }}
 
     - name: Check out repo
-      uses: actions/checkout@v4
+      uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with:
           token: ${{ steps.app-token.outputs.token }}
 
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
       with:
         python-version: 3.12