Use --driver-memory instead of --conf spark.driver.memory

According to Spark documentation, the configuration property `spark.driver.memory` has no effect in our case (we use the “client” deploy-mode):

>  In client mode, this config must not be set through the SparkConf directly in your application, because the driver JVM has already started at that point. Instead, please set this through the --driver-memory command line option or in your default properties file.

https://spark.apache.org/docs/latest/configuration.html

ansible/templates/submit-alternator-job.sh

@@ -12,5 +12,5 @@ time spark-submit --class com.scylladb.migrator.Migrator \
 --conf spark.scylla.config=/home/ubuntu/scylla-migrator/config.dynamodb.yml \
 --executor-memory $EXECUTOR_MEMORY \
 --executor-cores $EXECUTOR_CORES \
---conf spark.driver.memory=64G \
+--driver-memory 4G \
 /home/ubuntu/scylla-migrator/scylla-migrator-assembly.jar

ansible/templates/submit-cql-job.sh

@@ -19,7 +19,7 @@ time spark-submit --class com.scylladb.migrator.Migrator \
 
 #sometimes you will need a tuning for driver memory size
 #add this config to above to tune it:
-#  --conf spark.driver.memory=4G \
+#  --driver-memory 4G \
 
 # debug example
 #$SPARK_HOME/spark-submit --class com.scylladb.migrator.Migrator \