Revert "Define wxUSE_UNICODE on compiler command line in Unix builds too."

This fix only helps with building wxWidgets itself but doesn't help when
building user code using it, so revert it as we need another solution to this
problem anyhow.

This reverts r75536, see #15805.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75553 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

configure

@@ -35598,8 +35598,6 @@ if test "$wxUSE_FONTMAP" = "yes" ; then
 fi
 
 if test "$wxUSE_UNICODE" = "yes" ; then
-  CPPFLAGS="-DwxUSE_UNICODE=1 $CPPFLAGS"
-
   $as_echo "#define wxUSE_UNICODE 1" >>confdefs.h
 
 

configure.in

@@ -6397,8 +6397,6 @@ if test "$wxUSE_FONTMAP" = "yes" ; then
 fi
 
 if test "$wxUSE_UNICODE" = "yes" ; then
-  CPPFLAGS="-DwxUSE_UNICODE=1 $CPPFLAGS"
-
   AC_DEFINE(wxUSE_UNICODE)
 
   if test "$USE_WIN32" != 1; then