Fix a typo in the new S3TransferManager README (#2654)

Author: alexwlchan

services-custom/s3-transfer-manager/README.md

@@ -42,7 +42,7 @@ S3TransferManager transferManager =
 ```
 
 ### Download an S3 object to a file
-To download an object, you just need to provide the destion file path and the `GetObjectRequest` that should be used for the download.
+To download an object, you just need to provide the destination file path and the `GetObjectRequest` that should be used for the download.
 
 ```java
 Download download = 
@@ -62,4 +62,4 @@ Upload upload = transferManager.upload(b -> b.source(path)
 
 upload.completionFuture().join();
 
-```
+```