Update GitHub Action workflows to actions/checkout@v6 (master)

Author: TimWolla

.github/workflows/unit-tests.yml

@@ -35,7 +35,7 @@ jobs:
     timeout-minutes: 20
     steps:
       - name: git checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install dependencies
         run: |

.github/workflows/verify-bundled-files.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: git checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Detect changed files
         uses: dorny/paths-filter@v3