Cleanup: simplify some boolean expressions

src/signal.cpp

@@ -216,9 +216,7 @@ static inline bool CheckAddToTodoSet(TileIndex t1, DiagDirection d1, TileIndex t
 
 	assert(!_tbdset.IsIn(t1, d1)); // it really shouldn't be there already
 
-	if (_tbdset.Remove(t2, d2)) return false;
-
-	return true;
+	return !_tbdset.Remove(t2, d2);
 }