AMC args: cleanup add_automl_args arguments, fix documentation

examples/auto_compression/amc/amc_args.py

-def add_automl_args(argparser, arch_choices=None, enable_pretrained=False):
+def add_automl_args(argparser):
     """
-    Helper function to make it easier to add command-line arguments for AMC to any application.
+    Helper function which defines command-line arguments specific to AMC.
 
     Arguments:
         argparser (argparse.ArgumentParser): Existing parser to which to add the arguments