chore!: bump unit-mocha dependency versions (vuejs#5907)

Author: haoqunjiang

docs/migrations/migrate-from-v4.md

@@ -55,6 +55,11 @@ Please consider switching to ESLint. You can check out [`tslint-to-eslint-config
 
 * Cypress is updated from v3 to v5. See <https://docs.cypress.io/guides/references/migration-guide.html> for a detailed migration guide.
 
+### Unit-Mocha Plugin
+
+* Updated `mocha` from v6 to v7, please refer to the release notes of [mocha v7](https://github.com/mochajs/mocha/releases/tag/v7.0.0) for a complete list of breaking changes.
+* Updated `jsdom` from v15 to v16, the breaking changes are listed at <https://github.com/jsdom/jsdom/releases/tag/16.0.0>
+
 ### Internal Packages
 
 #### `@vue/cli-shared-utils`

packages/@vue/cli-plugin-unit-mocha/generator/index.js

@@ -9,8 +9,8 @@ module.exports = (api, options, rootOptions, invoking) => {
 
   api.extendPackage({
     devDependencies: {
-      '@vue/test-utils': isVue3 ? '^2.0.0-0' : '^1.0.3',
-      'chai': '^4.1.2'
+      '@vue/test-utils': isVue3 ? '^2.0.0-0' : '^1.1.0',
+      'chai': '^4.2.0'
     },
     scripts: {
       'test:unit': 'vue-cli-service test:unit'

packages/@vue/cli-plugin-unit-mocha/package.json

@@ -23,14 +23,14 @@
   "homepage": "https://github.com/vuejs/vue-cli/tree/dev/packages/@vue/cli-plugin-unit-mocha#readme",
   "dependencies": {
     "@vue/cli-shared-utils": "^4.5.5",
-    "jsdom": "^15.2.1",
+    "jsdom": "^16.4.0",
     "jsdom-global": "^3.0.2",
-    "mocha": "^6.2.2",
-    "mochapack": "^1.1.15"
+    "mocha": "^7.2.0",
+    "mochapack": "^2.0.2"
   },
   "devDependencies": {
-    "@vue/test-utils": "^1.0.3",
-    "chai": "^4.1.2"
+    "@vue/test-utils": "^1.1.0",
+    "chai": "^4.2.0"
   },
   "peerDependencies": {
     "@vue/cli-service": "^3.0.0 || ^4.0.0-0"