Applied auto-fixes from zizmor findings.

.github/workflows/python_matrix.yml

@@ -23,6 +23,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v5
+        with:
+          persist-credentials: false
       - id: set-matrix
         run: |
           python_versions=$(sed -n "s/^.*Programming Language :: Python :: \([[:digit:]]\+\.[[:digit:]]\+\).*$/'\1', /p" pyproject.toml | tr -d '\n' | sed 's/, $//g')
@@ -37,6 +39,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v5
+        with:
+          persist-credentials: false
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v6
         with: