update changelog

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Throw a parser error for `class:` directives with an empty class name ([#5858](https://github.com/sveltejs/svelte/issues/5858))
 * Fix extraneous store subscription in SSR mode ([#5883](https://github.com/sveltejs/svelte/issues/5883))
+* Don't emit update code for `class:` directives whose expression is not dynamic ([#5919](https://github.com/sveltejs/svelte/issues/5919))
 * Fix type inference for derived stores ([#5935](https://github.com/sveltejs/svelte/pull/5935))
 * Make parameters of built-in animations and transitions optional ([#5936](https://github.com/sveltejs/svelte/pull/5936))
 * Make `SvelteComponentDev` typings more forgiving ([#5937](https://github.com/sveltejs/svelte/pull/5937))