Random Word Replacement Probability
Hi,

It appears that the token masking function replaces tokens with random words 50% of the time instead of the commented 10%. 

https://github.com/huggingface/transformers/blob/709c86b5a925f1efe650e24ee8b1f52bdc5a3acb/src/transformers/data/data_collator.py#L381
Nevermind, didn't see the not for replaced indices so it's 50% of the remaining 20% after masking