Remove spurious MSVC check around wxDF_HTML code in wxMSW.

For some reason, support for wxDF_HTML in clipboard code was disabled for
non-MSVC compilers. Enable it now as it's not compiler-specific at all.

See #16297.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76632 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775