electra is added to onnx supported model (#15084)

* electra is added to onnx supported model

* add google/electra-base-generator for test onnx module

Co-authored-by: Lewis Tunstall <lewis.c.tunstall@gmail.com>

tests/test_onnx_v2.py

@@ -174,6 +174,7 @@ PYTORCH_EXPORT_MODELS = {
     ("ibert", "kssteven/ibert-roberta-base"),
     ("camembert", "camembert-base"),
     ("distilbert", "distilbert-base-cased"),
+    ("electra", "google/electra-base-generator"),
     ("roberta", "roberta-base"),
     ("xlm-roberta", "xlm-roberta-base"),
     ("layoutlm", "microsoft/layoutlm-base-uncased"),