docs: update client configuration documentation (#7345)

example appears to be copied from useDaulstackEndpoint without changing the comment

Author: mrgum

supplemental-docs/CLIENTS.md

@@ -692,7 +692,7 @@ This is a simple `boolean` setting that is present in most SDK Clients.
 It is used in endpoint resolution.
 
 ```ts
-// Example: setting useDualstackEndpoint
+// Example: setting useFipsEndpoint
 new S3Client({
   useFipsEndpoint: false,
 });