fixed spelling error in testing.mdx (#20220)

docs/source/en/testing.mdx

@@ -178,7 +178,7 @@ pytest -k "test and ada" tests/test_optimization.py
 ```
 ### Run documentation tests 
 
-In order to test whether the documentation examples are correct, you should checkt that the `doctests` are passing. 
+In order to test whether the documentation examples are correct, you should check that the `doctests` are passing. 
 As an example, let's use [`WhisperModel.forward`'s docstring](https://github.com/huggingface/transformers/blob/main/src/transformers/models/whisper/modeling_whisper.py#L1017-L1035): 
 
 ```python