build(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install Python
         uses: actions/setup-python@v5
@@ -52,7 +52,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5
@@ -86,7 +86,7 @@ jobs:
     if: ${{ github.ref_type == 'tag' }}
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0