docs: rename Unreleased section to Upcoming in release notes

Author: AustinBenoit

release_build_files/readme.md

@@ -613,7 +613,7 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
-### Unreleased
+### Upcoming
 - Changes
     - Auth (Desktop): Fixed log spam and high CPU utilization when offline by moving `USE_AUTH_EMULATOR` environment variable check to initialization and eliminating per-request logging (#1629).