chore: release 1.2.1 (#227)

* updated CHANGELOG.md

* updated package.json

* updated samples/package.json

Author: yoshi-automation

dataproc/package.json

@@ -14,7 +14,7 @@
     "test": "mocha system-test --timeout 60000"
   },
   "dependencies": {
-    "@google-cloud/dataproc": "^1.2.0"
+    "@google-cloud/dataproc": "^1.2.1"
   },
   "devDependencies": {
     "chai": "^4.2.0",