chore: update spark-connect-client to 3.5.6

Author: razvan

spark-connect-client/versions.py

@@ -1,6 +1,6 @@
 versions = [
     {
-        "product": "3.5.5",
+        "product": "3.5.6",
         "spark-k8s": "3.5.5",
         "java-base": "17",
         "python": "3.11",