APNGでもMIME typeはimage/pngにするように (#5100)

* APNGでもMIME typeはimage/pngにするように

* Revert "APNGでもMIME typeはimage/pngにするように"

This reverts commit e579eb2bf4.

* APNGはファイル送信時のみimage/pngにするように

src/services/drive/add-file.ts

@@ -207,6 +207,8 @@ export async function generateAlts(path: string, type: string, generateWeb: bool
  * Upload to ObjectStorage
  */
 async function upload(key: string, stream: fs.ReadStream | Buffer, type: string, filename?: string) {
+	if (type === 'image/apng') type = 'image/png';
+
 	const meta = await fetchMeta();
 
 	const minio = new Minio.Client({