Clarify body buffered when chunk_size set to None

This commit addresses #4504 (comment)

Author: ysaito1001

.changelog/1769635097.md

@@ -23,7 +23,7 @@ let client = aws_sdk_s3::Client::from_conf(config);
 ```
 
 ```
-// Disable chunking (send entire content as one chunk)
+// Disable chunking (buffers entire body in memory and sends it as one chunk)
 let config = aws_sdk_s3::Config::builder()
     .chunk_size(None)
     .build();

aws/codegen-aws-sdk/src/main/kotlin/software/amazon/smithy/rustsdk/AwsChunkedContentEncodingDecorator.kt

@@ -105,7 +105,7 @@ private class AwsChunkedConfigCustomization(
                         /// ## }
                         /// ```
                         ///
-                        /// ## Example - No chunking
+                        /// ## Example - No chunking (buffers entire body in memory)
                         /// ```no_run
                         /// ## use aws_sdk_s3::{Client, Config};
                         /// ## async fn example(client: Client) -> Result<(), Box<dyn std::error::Error>> {