Undo MIME type change of r74120.

Undo the temporary hack which was required to commit the non-UTF-8 file. In
the future the commit hook will be updated to relax the check for this file so
it won't be necessary any longer.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74125 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775