bug#38457: 27.0.50; dabbrev-expand regression due to message change

[Juri Linkov]

>> +(defcustom minibuffer-message-clear-timeout 2
>
> Hey now, shouldn't this be nil by default?

But Eli said:

  I won't object as long as the default for Emacs 27 is as in the 2nd
  variant.

where the 2nd variant was:

  after-input=t   after-timeout=2 - clear either on input or after timeout

Or was it zero-based numbering meaning the 3rd variant on 1-based numbering?

I'm fine with either default value.