i18n(ja): Update middleware.mdx for v3 (#4412)

Co-authored-by: Yan Thomas <[email protected]>

src/content/docs/ja/guides/middleware.mdx

@@ -44,7 +44,7 @@ const data = Astro.locals;
 
 ```ts
 // src/middleware.ts
-import { defineMiddleware } from "astro/middleware";
+import { defineMiddleware } from "astro:middleware";
 
 // `context`と`next`は自動的に型付けされます
 export const onRequest = defineMiddleware((context, next) => {
@@ -136,7 +136,7 @@ export const onRequest = async (context, next) => {
 [`sequence()`](#sequence)を使用して、複数のミドルウェアを指定した順序で連結できます。
 
 ```js title="src/middleware.js"
-import { sequence } from "astro/middleware";
+import { sequence } from "astro:middleware";
 
 async function validation(_, next) {
     console.log("validationリクエスト");