Correct example of wxRegKey use in its documentation.

Correct example of wxRegKey use in its documentation.

Don't check for the key existence, it ought to exist if we create it like
this.

Also don't allocate wxRegKey object on the heap unnecessarily.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66932 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775