PCSX2-WX: Increment max ISO count in recent ISO list

The default 12 is rather low and won't suffice for most cases, updating
it to 20 to give some extra space for additional ISOs. Incrementing it
to an even higher value might not be so good as it consumes lots of
vertical space, not a nice idea for people with smaller screens.

pcsx2/gui/AppConfig.cpp

@@ -535,7 +535,7 @@ AppConfig::AppConfig()
 {
 	LanguageId			= wxLANGUAGE_DEFAULT;
 	LanguageCode		= L"default";
-	RecentIsoCount		= 12;
+	RecentIsoCount		= 20;
 	Listbook_ImageSize	= 32;
 	Toolbar_ImageSize	= 24;
 	Toolbar_ShowLabels	= true;