fix typo in gradient_checkpointing arg (#12855)

help for `ModelArguments.gradient_checkpointing` should be
"If True, use gradient checkpointing to save memory
at the expense of slower backward pass."
not "Whether to freeze the feature extractor layers of the model."
(which is duplicated from `freeze_feature_extractor` arg)

examples/research_projects/wav2vec2/run_asr.py

@@ -55,7 +55,10 @@ class ModelArguments:
         default=True, metadata={"help": "Whether to freeze the feature extractor layers of the model."}
     )
     gradient_checkpointing: Optional[bool] = field(
-        default=False, metadata={"help": "Whether to freeze the feature extractor layers of the model."}
+        default=False,
+        metadata={
+            "help": "If True, use gradient checkpointing to save memory at the expense of slower backward pass."
+        },
     )
     verbose_logging: Optional[bool] = field(
         default=False,

examples/research_projects/wav2vec2/run_pretrain.py

@@ -51,7 +51,10 @@ class ModelArguments:
         default=True, metadata={"help": "Whether to freeze the feature extractor layers of the model."}
     )
     gradient_checkpointing: Optional[bool] = field(
-        default=False, metadata={"help": "Whether to freeze the feature extractor layers of the model."}
+        default=False,
+        metadata={
+            "help": "If True, use gradient checkpointing to save memory at the expense of slower backward pass."
+        },
     )
     verbose_logging: Optional[bool] = field(
         default=False,