Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/lint-reuse.yml

@@ -10,6 +10,6 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: REUSE Compliance Check
       uses: fsfe/reuse-action@v5

.github/workflows/package.yml

@@ -20,7 +20,7 @@ jobs:
   package:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Prepare
         run: |