UI: Fix compiler warning when WIN32 is not defined

Fix unused parameter warning.

UI/window-basic-interaction.cpp

@@ -202,6 +202,8 @@ bool OBSBasicInteraction::nativeEvent(const QByteArray &, void *message, long *)
 			display->OnDisplayChange();
 		}
 	}
+#else
+	UNUSED_PARAMETER(message);
 #endif
 
 	return false;