Mk/bsd.wx.mk: Revert and fix

Version 2.8 was removed without proper testing of the tree. The removal
of 2.8 has created multiple BROKEN ports with BROKEN INDEX. The proper
sequence should be removal of the consumers and then removing the
depricated version.

Approved by: portmgr (just-fix-it)
Fixes: ba3f1e0 remove wxgtk28 in USE_WX