Fix warning situation: UserWarning: max_length is ignored when padding=True" (#13829)
* Removed wrong warning
* Raise a warning when `max_length` is given with wrong `truncation`
* Update the error message
* Update the warning message
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>