Clarify S3 get params

The get parameters that control teleport's interaction with an S3 endpoint give the impression that this is some kind of `s3://` URL standard. This is not the case, so calling that out should help clarify.

docs/pages/setup/reference/backends.mdx

@@ -233,7 +233,7 @@ teleport:
 The AWS authentication settings above can be omitted if the machine itself is
 running on an EC2 instance with an IAM role.
 
-The optional `GET` parameters shown below control how Teleport interacts with an S3 endpoint, including S3-compatible endpoints.
+The optional `GET` parameters shown below are teleport-specific options to configure how Teleport interacts with an S3 endpoint, including S3-compatible endpoints.
 
 `s3://bucket/path?region=us-east-1&endpoint=mys3.example.com&insecure=false&disablesse=false&acl=private`