chore: typo fix in cli README.md (#29390)

### Reason for this change

I was reading the documentation and found a small typo to be fixed.

### Description of changes

Fixed the typo

### Description of how you validated changes

It's just a README

### Checklist
- [X] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: armmanvaillancourt

packages/aws-cdk/README.md

@@ -128,7 +128,7 @@ $ cdk synth
 $ # Synthesize cloud assembly for StackName, but don't include dependencies
 $ cdk synth MyStackName --exclusively
 
-$ # Synthesize cloud assembly for StackName, but don't cloudFormation template output to STDOUT
+$ # Synthesize cloud assembly for StackName, but don't write CloudFormation template output to STDOUT
 $ cdk synth MyStackName --quiet
 ```