Fix previewImg url

Author: fhammerschmidt

markdown-pages/blog/release-12-0-0.mdx

@@ -1,7 +1,7 @@
 ---
 author: rescript-team
 date: "2025-11-25"
-previewImg: /static/blog/compiler_release_12_0.webp
+previewImg: /blog/compiler_release_12_0.webp
 badge: release
 title: "Announcing ReScript 12"
 description: |