Update API_TEMPLATE.md (opensearch-project#4261)

Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

Author: kolchfa-aws

templates/API_TEMPLATE.md

@@ -82,7 +82,7 @@ The following table lists all response fields.
 
 | Field | Data type | Description |
 | :--- | :--- | :--- |
-| `response_field` | Type | Required field description. |
+| `response_field` | Type | Response field description. |
 
 ## Required permissions