chore: release 1.2.0 (#128)

* updated CHANGELOG.md [ci skip]

* updated package.json [ci skip]

* updated samples/package.json [ci skip]

Author: yoshi-automation

scheduler/package.json

@@ -14,7 +14,7 @@
     "test": "mocha --timeout 10000 --exit"
   },
   "dependencies": {
-    "@google-cloud/scheduler": "^1.1.4",
+    "@google-cloud/scheduler": "^1.2.0",
     "body-parser": "^1.18.3",
     "express": "^4.16.4"
   },