Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/maven.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
     - name: Set up JDK 21
       uses: actions/setup-java@f2beeb24e141e01a676f977032f5a29d81c9e27e # v5
       with: