Update CI for Neo4j 5.x to test on 5.7 and 5.6

Author: knutwalker

.github/workflows/checks.yml

@@ -106,7 +106,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        neo4j: ["5.5", "4.4", "4.3", "4.2", "4.1"]
+        neo4j: ["5.7", "5.6", "4.4", "4.3", "4.2", "4.1"]
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code