Clarify docs for Observable::complete

Reviewed By: kassens

Differential Revision: D27625877

fbshipit-source-id: e8e4580246942c9ac5f5308df7ecfc4f0bbbd5ce

website/docs/api-reference/relay-runtime/fetch-query.md

@@ -62,7 +62,7 @@ fetchQuery<AppQuery>(
         * Arguments:
             * `observer`: Object that specifies observer functions for different events occurring on the network request observable. May specify the following event handlers as keys in the observer object:
                 * `start`: Function that will be called when the network requests starts. It will receive a single `subscription` argument, which represents the subscription on the network observable.
-                * `complete`: Function that will be called when the network request is complete
+                * `complete`: Function that will be called if and when the network request completes successfully.
                 * `next`: Function that will be called every time a payload is received from the network. It will receive a single `data` argument, which represents a snapshot of the query data read from the Relay store at the moment a payload was received from the server.
                 * `error`:  Function that will be called if an error occurs during the network request. It will receive a single `error` argument, containing the error that occurred.
                 * `unsubscribe`: Function that will be called whenever the subscription is unsubscribed. It will receive a single `subscription` argument, which represents the subscription on the network observable.