List 26.3.0 release on upgrade page

Author: yoshiokatsuneo

src/pages/kb/open-source/admin-guide/how-to-upgrade.md

@@ -21,7 +21,8 @@ During each migration, check the [releases page](https://github.com/getredash/re
 Below is a table of recent docker release images for your reference:
 
 | released_at | version | docker_image                |
-| ----------- | ------- | --------------------------- |
+|-------------|---------|-----------------------------|
+| 2026-03-02  | 26.3.0  | redash/redash:26.3.0        |
 | 2025-08-01  | 25.8.0  | redash/redash:25.8.0        |
 | 2025-01-08  | 25.1.0  | redash/redash:25.1.0        |
 | 2021-12-24  | 10.1.0  | redash/redash:10.1.0.b50633 |