Add release date for 5.0.0b1

Author: timgraham

docs/source/releases/5.0.x.rst

@@ -5,7 +5,7 @@ Django MongoDB Backend 5.0.x
 5.0.0 beta 1
 ============
 
-*Unreleased*
+*February 26, 2025*
 
 - Backward-incompatible:
   :class:`~django_mongodb_backend.fields.ObjectIdAutoField` no longer accepts