chore: prep release for systemtest v1.3.0 (#24968)

Author: technicallyty

systemtests/CHANGELOG.md

@@ -36,7 +36,11 @@ Ref: https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.j
 
 ## [Unreleased]
 
-## [v1.2.0] -  2025-04-24
+## [v1.3.0] - 2025-07-23
+
+* [#24962](https://github.com/cosmos/cosmos-sdk/pull/24962) Allow chain id to be configured via `--chain-id` flag.
+
+## [v1.2.0] - 2025-04-24
 
 * SDK v0.53.x support.