chore: update changelog

Author: dervoeti

CHANGELOG.md

@@ -4,6 +4,13 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Changed
+
+- Set `maxSurge=1` and `maxUnavailable=0` on the OPA DaemonSet rolling update strategy to eliminate
+  availability gaps during rolling updates ([#819]).
+
+[#819]: https://github.com/stackabletech/opa-operator/pull/819
+
 ## [26.3.0] - 2026-03-16
 
 ## [26.3.0-rc1] - 2026-03-16