Add an ignore for the eslint error

babel-eslint 10.0.2 kicks up an error erroneously suggesting the
variables in the loop are unused. This wraps that section and tells
eslint to ignore it's erroneous error.

When we upgrade to 10.0.3, we can undo this.

frontend/src/Common.js

@@ -202,6 +202,9 @@ export const ShowValidationErrors = ({ errors, resetAndReload }) => {
 export const parseQueryString = qs => {
   const searchParams = new URLSearchParams(qs);
   const parsed = {};
+  // NOTE(willkg): babel-eslint 10.0.2 erroneously kicks up this error. Once we
+  // upgrade to 10.0.3, we can get rid of this.
+  /* eslint-disable no-unused-vars */
   for (let [key, value] of searchParams) {
     const already = parsed[key];
     if (already === undefined) {
@@ -212,6 +215,7 @@ export const parseQueryString = qs => {
       parsed[key] = [already, value];
     }
   }
+  /* eslint-enable no-unused-vars */
   return parsed;
 };