refactor: modernize the sample tests (#265)

Author: JustinBeckwith

packages/google-cloud-speech/samples/package.json

@@ -1,6 +1,5 @@
 {
   "name": "nodejs-docs-samples-speech",
-  "version": "0.0.1",
   "private": true,
   "license": "Apache-2.0",
   "author": "Google Inc.",
@@ -9,7 +8,7 @@
     "node": ">=8"
   },
   "scripts": {
-    "test": "mocha system-test/*.test.js --timeout 600000"
+    "test": "mocha system-test --timeout 600000"
   },
   "dependencies": {
     "@google-cloud/speech": "^2.1.1",
@@ -18,10 +17,9 @@
     "yargs": "^12.0.0"
   },
   "devDependencies": {
-    "@google-cloud/nodejs-repo-tools": "^3.0.0",
+    "chai": "^4.2.0",
+    "execa": "^1.0.0",
     "mocha": "^5.2.0",
-    "proxyquire": "^2.0.1",
-    "sinon": "^7.0.0",
     "uuid": "^3.3.0"
   }
 }