Update doc, call out that submit_app is translated to code on the RunArgs object

Author: Payton Staub

src/sagemaker/spark/processing.py

@@ -739,7 +739,8 @@ def get_run_args(
 
         Args:
             submit_app (str): Path (local or S3) to Python file to submit to Spark
-                as the primary application
+                as the primary application. This is translated to the `code`
+                property on the returned `RunArgs` object.
             submit_py_files (list[str]): List of paths (local or S3) to provide for
                 `spark-submit --py-files` option
             submit_jars (list[str]): List of paths (local or S3) to provide for
@@ -987,7 +988,8 @@ def get_run_args(
 
         Args:
             submit_app (str): Path (local or S3) to Python file to submit to Spark
-                as the primary application
+                as the primary application. This is translated to the `code`
+                property on the returned `RunArgs` object
             submit_class (str): Java class reference to submit to Spark as the primary
                 application
             submit_jars (list[str]): List of paths (local or S3) to provide for