Log the number of dancing link updates

src/sudoku/math.ts

@@ -161,7 +161,7 @@ export class SudokuMath {
   }
 
   generate(clues: number, attempts = Infinity, totalTime = Infinity) {
-    let [completed, updates] = this.generateComplete();
+    const [completed, updates] = this.generateComplete();
 
     const [header, dlxRows] = this.getDLXHeader(); // complete header - no candidates removed