Update repo to isort v5 (#6686)

* Run new isort

* More changes

* Update CI, CONTRIBUTING and benchmarks

tests/test_modeling_openai.py

@@ -25,12 +25,13 @@ from .test_modeling_common import ModelTesterMixin, ids_tensor
 
 if is_torch_available():
     import torch
+
     from transformers import (
-        OpenAIGPTConfig,
-        OpenAIGPTModel,
         OPENAI_GPT_PRETRAINED_MODEL_ARCHIVE_LIST,
-        OpenAIGPTLMHeadModel,
+        OpenAIGPTConfig,
         OpenAIGPTDoubleHeadsModel,
+        OpenAIGPTLMHeadModel,
+        OpenAIGPTModel,
     )