chore: mark cancelled-STX failure change as breaking (#9420)

## Explanation

Follow-up to #9400 (already merged). That PR changed the
`smart-transactions-controller` messenger requirement from
`TransactionController:updateTransaction` to
`TransactionController:failTransaction`. Adding/removing a required
allowed action is a **breaking change** for consumers — they must
delegate the new action to the controller messenger on the client side
(extension/mobile) or they get a type error.

The changelog entry was filed under `### Fixed`, which would have the
package cut as a patch release and silently break consumers on upgrade.
This recategorizes it under `### Changed` with a `**BREAKING:**` marker
so the next release is correctly a **major** version bump (`24.2.4` →
`25.0.0`), consistent with how allowed-action changes are documented
elsewhere in the monorepo (e.g. `AssetsControllerMessenger now requires
...` in assets-controller, `NftController allowed actions` in
assets-controllers).

No code changes — changelog only.

## References

- Follow-up to #9400
- Raised in review by @cryptodev-2s

## Changelog

### `@metamask/smart-transactions-controller`

- Recategorized the #9400 entry from `Fixed` to `Changed` and marked it
`BREAKING`; no functional change.

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
(N/A — changelog only)
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate (changelog)
- [x] I've highlighted breaking changes using the 'BREAKING' category
above as appropriate

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Documentation-only changelog edit with no code, tests, or runtime
behavior changes.
> 
> **Overview**
> Updates `@metamask/smart-transactions-controller` **Unreleased**
changelog only: the #9400 note about using
`TransactionController:failTransaction` instead of
`TransactionController:updateTransaction` when a smart transaction is
cancelled moves from `### Fixed` to `### Changed` and is labeled
**`BREAKING:`**, with explicit guidance that consumers must delegate the
new allowed action.
> 
> The separate `### Fixed` section is removed and the
`@metamask/messenger` bump stays under `### Changed`. **No runtime or
API code changes** in this PR—only semver/documentation so the next
release is treated as major for the messenger requirement change from
#9400.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
3bdac95. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: cloudonshore

packages/smart-transactions-controller/CHANGELOG.md

@@ -9,13 +9,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
-- Bump `@metamask/messenger` from `^1.2.0` to `^2.0.0` ([#9392](https://github.com/MetaMask/core/pull/9392))
-
-### Fixed
-
-- Fail the associated regular transaction via the new `TransactionController:failTransaction` action instead of `TransactionController:updateTransaction` when a smart transaction is cancelled ([#9400](https://github.com/MetaMask/core/pull/9400))
+- **BREAKING:** Fail the associated regular transaction via the new `TransactionController:failTransaction` action instead of `TransactionController:updateTransaction` when a smart transaction is cancelled ([#9400](https://github.com/MetaMask/core/pull/9400))
+  - Consumers must now grant the smart transactions controller messenger access to the `TransactionController:failTransaction` action (previously `TransactionController:updateTransaction`).
   - `updateTransaction` only patches state and does not emit transaction lifecycle events, so consumers that react to `transactionFailed`/`transactionStatusUpdated` (e.g. the bridge status controller and metrics) were never notified, leaving cancelled smart transactions — such as bridges — stuck as pending indefinitely.
-  - This requires consumers to grant the smart transactions controller messenger access to the `TransactionController:failTransaction` action (previously `TransactionController:updateTransaction`).
+- Bump `@metamask/messenger` from `^1.2.0` to `^2.0.0` ([#9392](https://github.com/MetaMask/core/pull/9392))
 
 ## [24.2.4]