chore: release 1.2.0 (#225)

* updated CHANGELOG.md [ci skip]

* updated package.json [ci skip]

* updated samples/package.json [ci skip]

Author: yoshi-automation

container/snippets/package.json

@@ -14,7 +14,7 @@
     "test": "mocha system-test --timeout 10000"
   },
   "dependencies": {
-    "@google-cloud/container": "^1.1.4"
+    "@google-cloud/container": "^1.2.0"
   },
   "devDependencies": {
     "chai": "^4.2.0",