Fix incorrect annotation name in upstream hashing configuration (#9617)

Author: lou-lan

docs/user-guide/nginx-configuration/annotations.md

@@ -239,7 +239,7 @@ To enable consistent hashing for a backend:
 
 `nginx.ingress.kubernetes.io/upstream-hash-by`: the nginx variable, text value or any combination thereof to use for consistent hashing. For example: `nginx.ingress.kubernetes.io/upstream-hash-by: "$request_uri"` or `nginx.ingress.kubernetes.io/upstream-hash-by: "$request_uri$host"` or `nginx.ingress.kubernetes.io/upstream-hash-by: "${request_uri}-text-value"` to consistently hash upstream requests by the current request URI.
 
-"subset" hashing can be enabled setting `nginx.ingress.kubernetes.io/upstream-hash-by-subset`: "true". This maps requests to subset of nodes instead of a single one. `upstream-hash-by-subset-size` determines the size of each subset (default 3).
+"subset" hashing can be enabled setting `nginx.ingress.kubernetes.io/upstream-hash-by-subset`: "true". This maps requests to subset of nodes instead of a single one. `nginx.ingress.kubernetes.io/upstream-hash-by-subset-size` determines the size of each subset (default 3).
 
 Please check the [chashsubset](../../examples/chashsubset/deployment.yaml) example.