Fix spark initialization in client/external.py

`enableHiveSupport` on itself is a method, and has to be called to get a builder from it.

python/hopsworks/client/external.py

@@ -123,7 +123,7 @@ def __init__(
             # are needed when the application starts (before user code is run)
             # So in this case, we can't materialize the certificates on the fly.
             _logger.debug("Running in Spark environment, initializing Spark session")
-            _spark_session = SparkSession.builder.enableHiveSupport.getOrCreate()
+            _spark_session = SparkSession.builder.enableHiveSupport().getOrCreate()
 
             self._validate_spark_configuration(_spark_session)
             with open(