docs: update changelog

Author: geoffrich

CHANGELOG.md

@@ -2,21 +2,12 @@
 
 ## [0.21.0](https://www.github.com/geoffrich/svelte-adapter-azure-swa/compare/v0.20.1...v0.21.0) (2025-03-04)
 
+This is a breaking change if you are deploying your own Azure functions alongside the Static Web App (`apiDir`) - see [the release notes](https://github.com/geoffrich/svelte-adapter-azure-swa/releases/tag/v0.21.0) for a migration guide.
 
 ### Features
 
 * switch to Azure Functions v4  ([#177](https://www.github.com/geoffrich/svelte-adapter-azure-swa/issues/177)) ([96e6067](https://www.github.com/geoffrich/svelte-adapter-azure-swa/commit/96e6067c50926c8328a5f78969ce74c304aaba75))
 
-## [Unreleased]
-
-### Features
-
-* **Breaking:** switch to Azure Functions v4:
-  * the function path has changed from `/api/__render` to `/api/sk_render` (v4 does not allow routes starting with underscores)
-  * see also [Migrate to version 4 of the Node.js programming model for Azure Functions](https://learn.microsoft.com/en-us/azure/azure-functions/functions-node-upgrade-v4) from the Azure docs
-
-
-
 ### [0.20.1](https://www.github.com/geoffrich/svelte-adapter-azure-swa/compare/v0.20.0...v0.20.1) (2024-07-13)