* and stop setting default values in python operator code, so defaults can be set at the server side.

This issue is just for the PR and questions from maintainers. 
airflow/providers/yandex/example_dags/example_yandexcloud_dataproc.py
'yarn.app.mapreduce.am.resource.mb': '2048',
            'yarn.app.mapreduce.am.command-opts': '-Xmx2048m',
            'mapreduce.job.maps': '6',
        },
    )
    create_spark_job = DataprocCreateSparkJobOperator(
        task_id='create_spark_job',
        main_jar_file_uri='s3a://data-proc-public/jobs/sources/java/dataproc-examples-1.0.jar',
        main_class='ru.yandex.cloud.dataproc.examples.PopulationSparkJob',
        file_uris=[
            's3a://data-proc-public/jobs/sources/data/config.json',
        ],
        archive_uris=[
            's3a://data-proc-public/jobs/sources/data/country-codes.csv.zip',
        ],
        jar_file_uris=[
            's3a://data-proc-public/jobs/sources/java/icu4j-61.1.jar',
            's3a://data-proc-public/jobs/sources/java/commons-lang-2.6.jar',
            's3a://data-proc-public/jobs/sources/java/opencsv-4.1.jar',
            's3a://data-proc-public/jobs/sources/java/json-20190722.jar',
        ],
        args=[
            's3a://data-proc-public/jobs/sources/data/cities500.txt.bz2',
            f's3a://{S3_BUCKET_NAME_FOR_JOB_LOGS}/dataproc/job/results/${{JOB_ID}}',
        ],
        properties={
            'spark.submit.deployMode': 'cluster',
        },
    )
    create_pyspark_job = DataprocCreatePysparkJobOperator(