Don't increase button height in wxMSWButton::GetFittingSize().

Don't increase button height in wxMSWButton::GetFittingSize().

This is unnecessary and resulted in too high buttons in some cases for buttons
with images. As we increase the button height to at least the standard value
later in all code using function anyhow, it's not necessary to do anything
with the height inside it.

Now the buttons with an image get the same height whether they have the text
or not.

This change also gets rid of (completely arbitrary) decision to use 11/10 of
the label height when computing the fitting button size and it's always nice
to get rid of dirty hacks like this.

Closes #12924.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66893 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775