Refs #31265 -- Updated .eslintignore to match eslint tests

.eslintignore

@@ -2,3 +2,4 @@
 **/vendor/**/*.js
 django/contrib/gis/templates/**/*.js
 node_modules/**.js
+tests/**/*.js

Gruntfile.js

@@ -1,4 +1,6 @@
-var globalThreshold = 50;  // Global code coverage threshold (as a percentage)
+'use strict';
+
+const globalThreshold = 50; // Global code coverage threshold (as a percentage)
 
 module.exports = function(grunt) {
     grunt.initConfig({