remove unnused functions.

src/templates/components/PostList.tsx

@@ -1,9 +1,5 @@
 import type { PostMeta } from '@blog/models/PostMeta';
 
-function formatDate(date: Date): string {
-  return `${date.getFullYear()}-${date.getMonth()}-${date.getDay()}`;
-}
-
 export function PostList({ posts }: { posts: PostMeta[] }) {
   return(
     <ul>