refactor: refactoring imports

将来ESMに移行しやすいように
Related: #7658

なんかmochaが起動しなくなってるけど理由不明
すぐ直したい

src/server/api/stream/channels/admin.ts

@@ -1,5 +1,5 @@
 import autobind from 'autobind-decorator';
-import Channel from '../channel';
+import Channel from '../channel.js';
 
 export default class extends Channel {
 	public readonly chName = 'admin';