Change nightly build from hourly to nightly (daily at 00:00) (#28346)

Summary:
We initially added the nightly build test to run every hour, in order to more quickly validate it. Now that it has been validated we can run it every night as it is intended to do.

cc hramos

## Changelog

[General] [Changed] - Change nightly build from hourly to nightly
Pull Request resolved: #28346

Reviewed By: cpojer

Differential Revision: D20550143

Pulled By: hramos

fbshipit-source-id: 9487c6785684ad6ea7e877290d50a33118090a7f

.circleci/config.yml

@@ -746,7 +746,7 @@ workflows:
   nightly:
     triggers:
       - schedule:
-          cron: "0 * * * *"
+          cron: "0 0 * * *"
           filters:
             branches:
               only: