Update nightly to actually deploy nightly

Midnight on the nose (or 5 minutes either side, if we're following GitHub documentation) feels a suitably memorable delinator, in terms of knowing when new nightly builds are landing!

.github/workflows/deploy-nightly.yml

@@ -3,7 +3,7 @@ name: Build & Publish Nightly
 on:
   workflow_dispatch:
   schedule:
-    - cron: "0 12 * * *"
+    - cron: "0 0 * * *"
 
 jobs:
   deploy: