Bump actions/checkout to v6

Author: mrotteveel

.github/workflows/codeql.yml

@@ -48,7 +48,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/reuse-compliance.yml

@@ -16,6 +16,6 @@ jobs:
   reuse:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: REUSE Compliance Check
         uses: fsfe/reuse-action@v6

.github/workflows/run-tests.yml

@@ -20,7 +20,7 @@ jobs:
           version: '5.0.3'
           firebird_root_password: 'masterkey'
           firebird_conf: 'WireCrypt=Enabled,AuthServer=Srp256;Srp;Legacy_Auth,UserManager=Srp;Legacy_UserManager'
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Java 17
         uses: actions/setup-java@v4
         with: