Do you know this ...no?
Well, neither did I. So here goes.
Set-AutodiscoverVirtualDirectory -Identity 'autodiscover (default Web site)' -internalUrl ($null) -externalUrl ($null)
That wasn't hard, was it? :)
PS
HarriJaakkonen
:~/Blog/Posts>
cat ./how-to-set-exchange-autodiscovervirtua.html