documentation: error handling example is outdated for currentl graphql-java version

[Patrickkooijman]

What are you missing in the docs

The error-handling page shows an example which ends with a delegate call to handle other exceptions then MyException.`

return DataFetcherExceptionHandler.super.handleException(handlerParameters);

This default method was however deprecated and is removed in graphql-java 21.3, https://github.com/graphql-java/graphql-java/commit/1021219732d24866fb5957d8d8dc473b5d588f03