Update Node.js version in Readme (#1617)
Update Node.js version in Readme (#1617)

Please do not merge manually, we are trying out the auto-merge bot. 

@sofisl would the bot respect the `do-not-merge` label?
GoogleCloudPlatform/nodejs-docs-samples,GoogleCloudPlatform/nodejs-docs-samples,GoogleCloudPlatform/nodejs-docs-samples,GoogleCloudPlatform/nodejs-docs-samples