fix some README typos

This module installs the GCP Cloud SQL Proxy software and configures its

options. This module is a "define" in case you need to install more than

instance of the Cloud SQL Proxy service. For more information on

one instance of the Cloud SQL Proxy service. For more information on

configuration, see the [Cloud SQL Proxy Github

page](https://github.com/GoogleCloudPlatform/cloudsql-proxy).

## Examples

The `instances` is the only required parameter. It is an array to allow

multiple instances to be configured:

The parameter `instances` is the only one required. It is an array (this allows

multiple instances to be configured):

```

gcp_cloudsql_proxy { 'example1':

  instances => ["my-gcp-project:us-west1:mysql-1=tcp:3306"],