chore: Update README

Signed-off-by: Dillon Nys <24740863+dnys1@users.noreply.github.com>

Author: dnys1

README.md

@@ -7,7 +7,7 @@
 
 > [!WARNING]
 > Celest is in the process of being open-sourced. During this process, many of the previously valid links like [celest.dev]() will be
-> unavailable. We expect this process to be completed by the end of March 2025.
+> unavailable. We expect this process to be completed by the end of April 2025.
 
 Celest is the Flutter cloud platform. We enable Flutter and Dart developers to declaratively define their backend infrastructure in Dart.