Bump actions/checkout from 5 to 6

Author: dependabot[bot]

.github/workflows/publish.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v6

.github/workflows/tests.yml

@@ -20,7 +20,7 @@ jobs:
         - "3.14"
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
 
     - name: Setup Python
       uses: actions/setup-python@v6