ESLint one-var, no-var rules (#3239)

* fixed issues for eslint one-var and no-var rules

Co-authored-by: Joshi <simplyrender@gmail.com>
Co-authored-by: Andrew Henry <akhenry@gmail.com>

src/MCTSpec.js

@@ -26,11 +26,11 @@ define([
     'utils/testing'
 ], function (plugins, legacyRegistry, testUtils) {
     describe("MCT", function () {
-        var openmct;
-        var mockPlugin;
-        var mockPlugin2;
-        var mockListener;
-        var oldBundles;
+        let openmct;
+        let mockPlugin;
+        let mockPlugin2;
+        let mockListener;
+        let oldBundles;
 
         beforeEach(function () {
             mockPlugin = jasmine.createSpy('plugin');
@@ -109,7 +109,7 @@ define([
         });
 
         describe("setAssetPath", function () {
-            var testAssetPath;
+            let testAssetPath;
 
             beforeEach(function () {
                 openmct.legacyExtension = jasmine.createSpy('legacyExtension');