fix(deps): update dependency yargs to v12 (#63)

Author: renovate[bot]

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

@@ -14,15 +14,15 @@
     "test": "npm run cover"
   },
   "dependencies": {
-    "@google-cloud/dns": "0.7.2",
-    "yargs": "11.0.0"
+    "@google-cloud/dns": "^0.7.2",
+    "yargs": "^12.0.1"
   },
   "devDependencies": {
-    "@google-cloud/nodejs-repo-tools": "2.3.0",
-    "ava": "0.25.0",
-    "nyc": "12.0.2",
-    "proxyquire": "2.0.1",
-    "sinon": "6.0.1",
-    "uuid": "3.3.0"
+    "@google-cloud/nodejs-repo-tools": "^2.3.0",
+    "ava": "^0.25.0",
+    "nyc": "^12.0.2",
+    "proxyquire": "^2.0.1",
+    "sinon": "^6.0.1",
+    "uuid": "^3.3.0"
   }
 }