note Import API should not be called in parallel (#3419)

* note Import API should not be called in parallel

astro/src/content/docs/apis/users.mdx

@@ -339,7 +339,9 @@ The response for this API contains the information for the User that was reactiv
 
 ## Import Users
 
-This API is used to bulk import multiple Users into FusionAuth. Each User must have at least an **email** or a **username**. This request is useful for migrating data from an existing database into FusionAuth. Additionally, you can provide an Id for each User inside the JSON User object of the request body. When using this API you should import with batches of less than 10,000 users per request. After completing an import you should [reindex of the Elasticsearch database](/docs/lifecycle/manage-users/search/search#reindexing-elasticsearch) as well.
+This API is used to bulk import multiple Users into FusionAuth. Each User must have at least an **email** or a **username**. This request is useful for migrating data from an existing database into FusionAuth. Additionally, you can provide an Id for each User inside the JSON User object of the request body. When using this API, you should import with batches of less than 10,000 users per request. After completing an import, you should [reindex the Elasticsearch database](/docs/lifecycle/manage-users/search/search#reindexing-elasticsearch) as well.
+
+You should not make multiple calls to this API in parallel. Multiple sequential calls to this API are fine.
 
 ### Request