(DOCSP-53435) Update flex-cluster README

Author: antellezr-mdb

src/l1-resources/flex-cluster/README.md

@@ -9,15 +9,15 @@ The official [MongoDB Atlas](https://www.mongodb.com/) AWS CDK resource for Node
 
 ## Description
 
-The flex cluster resource provides access to your flex cluster configurations. The resource lets you create, edit and delete flex clusters. For more information, see [The MongoDB Atlas Flex Tier](https://www.mongodb.com/company/blog/product-release-announcements/dynamic-workloads-predictable-costs-mongodb-atlas-flex-tier).
+The flex cluster resource provides access to your flex cluster configurations and enable you to create, edit, and delete flex clusters. For more information, see [The MongoDB Atlas Flex Tier](https://www.mongodb.com/company/blog/product-release-announcements/dynamic-workloads-predictable-costs-mongodb-atlas-flex-tier).
 
 ## MongoDB Atlas API Docs
 
 For more information about the API refer to: [API Endpoints](https://www.mongodb.com/docs/atlas/reference/api-resources-spec/v2/#tag/Flex-Clusters)
 
 ## Usage
 
-In order to use this library, you will need to activate this AWS CloudFormation Registry type in your account. You can do this via the AWS Management Console or using the [AWS CLI](https://aws.amazon.com/cli/) using the following command:
+In order to use this library, you must activate the following AWS CloudFormation Registry type in your account. You can do this via the AWS Management Console or through the [AWS CLI](https://aws.amazon.com/cli/) using the following command:
 
 ```sh
 aws cloudformation activate-type \
@@ -59,6 +59,8 @@ const flexClusterRes = new CfnFlexCluster(this, 'FlexClusterResource', {
 });
 ```
 
+*Note:* Upgrades to or from flex clusters are currently unavailable. We expect to support upgrades to or from flex clusters in the forseeable future.
+
 ## Feedback
 
 This library is auto-generated and published to all supported programming languages by the [cdklabs/cdk-cloudformation] project based on the API schema published for `MongoDB::Atlas::FlexCluster`.