chore: remove unused date-fns (#7856)

Author: noritaka1166

package.json

@@ -30,7 +30,6 @@
     "@radix-ui/react-context-menu": "^2.1.5",
     "body-scroll-lock": "^3.1.3",
     "classnames": "^2.2.6",
-    "date-fns": "^2.16.1",
     "debounce": "^1.2.1",
     "github-slugger": "^1.3.0",
     "next": "15.1.0",

yarn.lock

@@ -2799,11 +2799,6 @@ data-view-byte-offset@^1.0.0:
     es-errors "^1.3.0"
     is-data-view "^1.0.1"
 
-date-fns@^2.16.1:
-  version "2.28.0"
-  resolved "https://registry.npmjs.org/date-fns/-/date-fns-2.28.0.tgz"
-  integrity sha512-8d35hViGYx/QH0icHYCeLmsLmMUheMmTyV9Fcm6gvNwdw31yXXH+O85sOBJ+OLnLQMKZowvpKb6FgMIQjcpvQw==
-
 debounce@^1.2.1:
   version "1.2.1"
   resolved "https://registry.npmjs.org/debounce/-/debounce-1.2.1.tgz"