tools: remove unneeded parentheses in doc/html.js

PR-URL: #16845
Ref: #16801 (comment)
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

tools/doc/html.js

@@ -466,7 +466,7 @@ function getId(text) {
   text = text.replace(/^_+|_+$/, '');
   text = text.replace(/^([^a-z])/, '_$1');
   if (idCounters.hasOwnProperty(text)) {
-    text += `_${(++idCounters[text])}`;
+    text += `_${++idCounters[text]}`;
   } else {
     idCounters[text] = 0;
   }