Remove redundant void from C++ sources (#1486)

diff --git a/util/hb-fc.cc b/util/hb-fc.cc
index cb89991..2fe0146 100644
--- a/util/hb-fc.cc
+++ b/util/hb-fc.cc
@@ -72,7 +72,7 @@
 }
 
 static hb_font_funcs_t *
-_hb_fc_get_font_funcs (void)
+_hb_fc_get_font_funcs ()
 {
   static const hb_font_funcs_t *fc_ffuncs;