Update CHANGELOG.md

Author: szokeasaurusrex

Diff for: CHANGELOG.md

@@ -2,9 +2,12 @@
 
 ## 2.5.1
 
-### Various fixes & improvements
+This change fixes a regression in our cron monitoring feature, which caused cron checkins not to be sent. The regression appears to have been introduced in version 2.4.0.
+
+**We recommend that all users, who use Cron monitoring and are currently running sentry-python ≥2.4.0, upgrade to this release as soon as possible!**
+
+### Other fixes & improvements
 
-- Revert "Refactor the Celery Beat integration (#3105)" (#3144) by @szokeasaurusrex
 - feat(tracing): Warn if not-started transaction entered (#3003) by @szokeasaurusrex
 - test(scope): Ensure `last_event_id` cleared (#3124) by @szokeasaurusrex
 - fix(scope): Clear last_event_id on scope clear (#3124) by @szokeasaurusrex