Aktualisiere GHA Actions auf aktuelle Versionen (#5)

Batch-Commit via webfactory/bfg9000#16

Author: mpdude

.github/workflows/tests.yml

@@ -18,7 +18,7 @@ jobs:
                 node-version: [ 20.x ]
 
         steps:
-            - uses: actions/checkout@v4
+            - uses: actions/checkout@v6
 
             - name: Use Node.js ${{ matrix.node-version }}
               uses: actions/setup-node@v3