deps: update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/publish.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/pytest.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Cloning repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0