Update repo to isort v5 (#6686)

* Run new isort

* More changes

* Update CI, CONTRIBUTING and benchmarks

tests/test_modeling_tf_gpt2.py

@@ -25,11 +25,12 @@ from .test_modeling_tf_common import TFModelTesterMixin, ids_tensor
 
 if is_tf_available():
     import tensorflow as tf
+
     from transformers.modeling_tf_gpt2 import (
-        TFGPT2Model,
-        TFGPT2LMHeadModel,
-        TFGPT2DoubleHeadsModel,
         TF_GPT2_PRETRAINED_MODEL_ARCHIVE_LIST,
+        TFGPT2DoubleHeadsModel,
+        TFGPT2LMHeadModel,
+        TFGPT2Model,
         shape_list,
     )