Xace: dont install xace.h and xacestr.h anymore

These aren't used by any drivers, so no need to keep them installed.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1556>

Xext/meson.build

@@ -37,7 +37,6 @@ endif
 
 if build_xace
     srcs_xext += 'xace.c'
-    hdrs_xext += ['xace.h', 'xacestr.h']
 endif
 
 if build_xf86bigfont