docs(ET-1813): add more for AWS_CA_BUNDLE

advocacy_docs/edb-postgres-ai/migration-etl/data-migration-service/getting_started/config_reader.mdx

@@ -176,6 +176,8 @@ The Apicurio client uses it to perform mTLS authentication with the `transporter
 ### `AWS_CA_BUNDLE (Optional)`
 This is only needed if you are using a self-signed certificate for the object storage. You need to set the path to the CA bundle file.
 
+You don't need to set this if you are using AWS S3 or s3 compatible storage with publicly-trusted CAs.
+
 ### `AWS_ENDPOINT_URL_S3`
 1) If you are using AWS S3, you can find the endpoint url in: https://docs.aws.amazon.com/general/latest/gr/s3.html