refactor: use explicit mocha imports (#505)

Author: JustinBeckwith

packages/google-cloud-vision/samples/.eslintrc.yml

@@ -1,4 +1,3 @@
 ---
 rules:
   no-console: off
-  node/no-missing-require: off

packages/google-cloud-vision/smoke-test/.eslintrc.yml

@@ -1,5 +1,3 @@
 ---
-env:
-  mocha: true
 rules:
   no-console: off

packages/google-cloud-vision/smoke-test/image_annotator_smoke_test.js

@@ -14,6 +14,8 @@
 
 'use strict';
 
+const {describe, it} = require('mocha');
+
 describe('ImageAnnotatorSmokeTest', () => {
   it('successfully makes a call to the service', done => {
     const vision = require('../src');

packages/google-cloud-vision/system-test/.eslintrc.yml

@@ -1,6 +1,4 @@
 ---
-env:
-  mocha: true
 rules:
   no-console: off
   node/no-unsupported-features/es-syntax: off

packages/google-cloud-vision/system-test/image_annotator_smoke_test.js

@@ -14,6 +14,8 @@
 
 'use strict';
 
+const {describe, it} = require('mocha');
+
 describe('ImageAnnotatorSmokeTest', () => {
   it('successfully makes a call to the service', done => {
     const vision = require('../src');

packages/google-cloud-vision/system-test/vision-v1p2beta1.js

@@ -14,6 +14,8 @@
 
 'use strict';
 
+const {describe, it} = require('mocha');
+
 describe('ImageAnnotatorSmokeTest', () => {
   it('successfully makes a call to the service', done => {
     const vision = require('../src');

packages/google-cloud-vision/system-test/vision.js

@@ -17,6 +17,7 @@
 'use strict';
 
 const assert = require('assert');
+const {describe, it, before, after} = require('mocha');
 const fs = require('fs');
 const path = require('path');
 const {Storage} = require('@google-cloud/storage');

packages/google-cloud-vision/test/.eslintrc.yml

@@ -15,6 +15,7 @@
 'use strict';
 
 const assert = require('assert');
+const {describe, it} = require('mocha');
 
 const visionModule = require('../src');
 

packages/google-cloud-vision/test/gapic-v1.js

@@ -15,6 +15,7 @@
 'use strict';
 
 const assert = require('assert');
+const {describe, it} = require('mocha');
 
 const visionModule = require('../src');