Backport of Update service.check.task definition to match code into release/1.1.x (#13132)

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website/content/docs/job-specification/service.mdx

@@ -281,7 +281,7 @@ scripts.
   check. Scripts are executed within the task's environment, and
   `check_restart` stanzas will apply to the specified task. For `checks` on group
   level `services` only. Inherits the [`service.task`][service_task] value if not
-  set.
+  set. May only be set for script or gRPC checks.
 
 - `timeout` `(string: <required>)` - Specifies how long Consul will wait for a
   health check query to succeed. This is specified using a label suffix like