SSA: fix go marker for listMapKey in the merge strategy

Ref: https://github.com/kubernetes/kube-openapi/blob/64514a1d5d596b96e6f957e2be275ae14d6b0804/pkg/generators/extension.go#L49-L50

Author: nikhita

content/en/docs/reference/using-api/api-concepts.md

@@ -644,7 +644,7 @@ in Go files or in the
 | Golang marker | OpenAPI extension | Accepted values | Description | Introduced in |
 |---|---|---|---|---|
 | `//+listType` | `x-kubernetes-list-type` | `atomic`/`set`/`map` | Applicable to lists. `atomic` and `set` apply to lists with scalar elements only. `map` applies to lists of nested types only. If configured as `atomic`, the entire list is replaced during merge; a single manager manages the list as a whole at any one time. If `granular`, different managers can manage entries separately. | 1.16          |
-| `//+listMapKeys` | `x-kubernetes-list-map-keys` | Slice of map keys that uniquely identify entries for example `["port", "protocol"]` | Only applicable when `+listType=map`. A slice of strings whose values in combination must uniquely identify list entries. | 1.16 |
+| `//+listMapKey` | `x-kubernetes-list-map-keys` | Slice of map keys that uniquely identify entries for example `["port", "protocol"]` | Only applicable when `+listType=map`. A slice of strings whose values in combination must uniquely identify list entries. While there can be multiple keys, `listMapKey` is singular because keys need to be specified individually in the Go type. | 1.16 |
 | `//+mapType` | `x-kubernetes-map-type` | `atomic`/`granular` | Applicable to maps. `atomic` means that the map can only be entirely replaced by a single manager. `granular` means that the map supports separate managers updating individual fields. | 1.17 |
 | `//+structType` | `x-kubernetes-map-type` | `atomic`/`granular` | Applicable to structs; otherwise same usage and OpenAPI annotation as `//+mapType`.| 1.17 |