Added an error when `temperature` is defined but `do_sample` is False.
# What does this PR do?

This is to prevent the possibility that people think that setting a temperature is enough to get sampling behavior.
I found this confusing at first.

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case): No, but is kind of a similar idea, in that it makes things more clear.
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section? Quickly I must admit.
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? No.
- [N/A] Did you make sure to update the documentation with your changes? N/A, this is to make implicit behavior more clear.
- [ ] Did you write any new necessary tests?: N/A


## Who can review?
@patrickvonplaten
@patrickvonplaten Added as an edit, not sure if it pinged you.<|||||>The test that fails has nothing to do with this change<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.