Summarization also supports MT5ForConditionalGeneration
The [README.md](https://github.com/huggingface/transformers/blob/master/examples/pytorch/summarization/README.md) of the summarization examples sais it supports `T5ForConditionalGeneration` IMO `MT5ForConditionalGeneration` should be added - right?

Tagging @sgugger and @sshleifer ...
And @patil-suraj<|||||>Yes, you are right!

We could also add it  in the[ translation readme](https://github.com/huggingface/transformers/blob/master/examples/pytorch/translation/README.md) as well.

Feel free to open a PR :)<|||||>> Feel free to open a PR :)

see #11961

<|||||>Fixed by #11961