[Cleanup] Mask GM Show Buff message behind EntityVariable (#4419)

* [Cleanup] Mask GM Show Buff message behind EntityVariable

Removes the spam of "Your GM flag allows you to always see your targets' buffs." for GMs every time a buff lands on a target.

It will now lock to an Entity Variable and only show once per zone.

* Convert string to constexpr

* Switch from string to char

zone/client_packet.cpp

@@ -793,6 +793,8 @@ void Client::CompleteConnect()
 		parse->EventPlayer(EVENT_ENTER_ZONE, this, "", 0);
 	}
 
+	DeleteEntityVariable(SEE_BUFFS_FLAG);
+
 	// the way that the client deals with positions during the initial spawn struct
 	// is subtly different from how it deals with getting a position update
 	// if a mob is slightly in the wall or slightly clipping a floor they will be