Fix shadow performance regression due to force update

broken by: b861f0c5c5

src/client/shadows/dynamicshadows.h

@@ -85,6 +85,7 @@ public:
 		return mapRes;
 	}
 
+	/// If true, shadow map needs to be invalidated due to frustum change
 	bool should_update_map_shadow{true};
 
 	void commitFrustum();