Update actions/checkout action to v6 (#133)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/deploy.yml

@@ -7,7 +7,7 @@ jobs:
   deploy:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v5

.github/workflows/python-package.yml

@@ -17,7 +17,7 @@ jobs:
           - "3.13"
           - "3.14"
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Set up Python ${{ matrix.python }}
       uses: actions/setup-python@v5