Use The Same Gradle Version For Each Example

[opticyclic]

android-example uses gradle 4.10.1
hello-world-groovy uses gradle 5.5
hello-world-java, neo4j-musicians and views-and-forms-java use gradle 6.1
hello-world-kotlin uses gradle 6.9-rc-2
hello-world-lambda and petstore use gradle 4.8
websocket-chat uses gradle 5.1.1

Use the same version of gradle for each example so I don't have to download 6 gradle distributions just to try them out.