Replace wxFONTFAMILY_DEFAULT with wxFONTFAMILY_SWISS when comparing fonts.

Otherwise comparison always failed as no existing fonts had
wxFONTFAMILY_DEFAULT as their family in all ports except wxOSX, which does
keep wxFONTFAMILY_DEFAULT.

Closes #15410.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74660 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775