Fix the CHANGELOG (#387)

The upgrade to Polkadot-SDK 1.13 accidentally put the changes under the
1.2.8 release, while these changes are actually not yet released.

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- [ ] Does not require a CHANGELOG entry

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Co-authored-by: Dónal Murray <[email protected]>

CHANGELOG.md

@@ -4,7 +4,7 @@ Changelog for the runtimes governed by the Polkadot Fellowship.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
-## [1.2.8] 03.07.2024
+## [Unreleased]
 
 ### Added
 
@@ -36,9 +36,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
-- Snowbridge: Sync headers on demand ([polkadot-fellows/runtimes#345](https://github.com/polkadot-fellows/runtimes/pull/365))
-- Polkadot chains: allow arbitrary XCM execution ([polkadot-fellows/runtimes#345](https://github.com/polkadot-fellows/runtimes/pull/345)).
-
 #### From [#322](https://github.com/polkadot-fellows/runtimes/pull/322):
 
 - AdaptPrice trait is now price controlled ([SDK v1.13 #4521](https://github.com/paritytech/polkadot-sdk/pull/4521)).
@@ -103,6 +100,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 - Upgrade dependencies to the [[email protected]](https://github.com/paritytech/polkadot-sdk/releases/tag/polkadot-v1.13.0) release ([polkadot-fellows/runtimes#332](https://github.com/polkadot-fellows/runtimes/pull/332))
 
+## [1.2.8] 03.07.2024
+
+### Changed
+
+- Snowbridge: Sync headers on demand ([polkadot-fellows/runtimes#365](https://github.com/polkadot-fellows/runtimes/pull/365))
+- Polkadot chains: allow arbitrary XCM execution ([polkadot-fellows/runtimes#345](https://github.com/polkadot-fellows/runtimes/pull/345)).
+
 Note: This release only affects the following runtimes and is not a full system release:
 
 - Polkadot Relay Chain