Fix QFontCache::Key comparison for custom font fallbacks case

Just a C&P typo, of course we have to compare lists, not their sizes.

Change-Id: I40542035b87f5bb8d75207cb02c0826cc3a2a413
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/gui/text/qfont_p.h

@@ -251,7 +251,7 @@ public:
             return script == other.script
                     && screen == other.screen
                     && multi == other.multi
-                    && (!multi || def.fallBackFamilies.size() == other.def.fallBackFamilies.size())
+                    && (!multi || def.fallBackFamilies == other.def.fallBackFamilies)
                     && def == other.def;
         }
     };