Apply suggestions from code review

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

api-spec/messagingapi_events_send_by_id.yaml

@@ -21,7 +21,7 @@ get: # get_messaging_v1_events_send_by_id
             $ref: './schemas/apitypes.yaml#/SendStatus'
     '404':
       description: No send events buffered for the given request id.
-    '4XX':
+    '400':
       description: Bad request.
     '5XX':
       description: Unexpected error.

api-spec/messagingapi_subscriptions.yaml

@@ -1,7 +1,7 @@
 # /messaging/v1/subscriptions:
 post: # post_messaging_v1_subscriptions
   summary: Subscribe the messaging client to an array of content topics
-  description: Subscribe the messaging client to an array of Content topics.
+  description: Subscribe the messaging client to an array of content topics.
   operationId: postMessagingSubscriptions
   tags:
     - messaging
@@ -26,7 +26,7 @@ post: # post_messaging_v1_subscriptions
 
 delete: # delete_messaging_v1_subscriptions
   summary: Unsubscribe the messaging client from an array of content topics
-  description: Unsubscribe the messaging client from an array of Content topics.
+  description: Unsubscribe the messaging client from an array of content topics.
   operationId: deleteMessagingSubscriptions
   tags:
     - messaging

api-spec/schemas/apitypes.yaml

@@ -346,7 +346,7 @@ MessagingSendResponse:
   properties:
     requestId:
       type: string
-      description: Correlates the send with its MessageSent / MessageError events.
+      description: Correlates the send with subsequent send events (sent/propagated/error).
   required:
     - requestId