CMR-10455: Update subscription doc on subscription edge case limit (nasa#2236)

* update subscription doc

* fix wording

Author: jmaeng72

ingest-app/docs/api.md

@@ -1169,6 +1169,11 @@ For NRT Notification subscriptions to be used there are three new fields that ar
         </ul>
 </ul>
 
+IMPORTANT: There is limit to creating and updating subscriptions related to the specific scenario highlighted below:
+Currently, if <User 1> creates a subscription to <Collection 1> and then <User 2> creates a different subscription 
+to the same <Collection 1> for the same queue, it will overwrite the first subscription for that specific queue.
+So please, have each queue have only one agreed upon subscription.
+
 ##### NRT Notification Subscription POST Request
 
 ```
@@ -1228,6 +1233,11 @@ If a native-id is provided in a POST, and a subscription already exists for that
 
 PUT requests should be used for updating subscriptions. Creating subscriptions with PUT may be deprecated in the future. All PUT requests require a native-id to be part of the request URL.
 
+IMPORTANT: There is limit to creating and updating subscriptions related to the specific scenario highlighted below:
+Currently, if <User 1> creates a subscription to <Collection 1> and then <User 2> creates a different subscription
+to the same <Collection 1> for the same queue, it will overwrite the first subscription for that specific queue.
+So please, have each queue have only one agreed upon subscription.
+
 ##### Create Batch Notification subscription with %CMR-ENDPOINT%/subscriptions/<native-id> URL
 ```
 curl -XPUT \