Small update to Update 0194.md (#1177)

add hyperlink to related AIP-4221 in the note about client and bidi streaming

Co-authored-by: Noah Dietz <noahdietz@users.noreply.github.com>

Author: leahecole

aip/general/0194.md

@@ -28,6 +28,7 @@ Clients **should not** automatically retry requests in which repeated runs
 would cause unintended state changes.
 
 **Note:** This AIP does not cover client streaming or bi-directional streaming.
+**Note:** Client side retry behavior for the client libraries is found in [AIP-4221](../client-libraries/4221.md).
 
 ### Retryable codes