fix(backend): フォローリクエストを作成する際に既存のものは削除するように (#13588)

* fix: delete old follow request (if exists) before creating new

(cherry picked from commit ea948ccadc7eace1fcace176c9c070b2a9b46f56)

* Update Changelog

* Update Changelog

---------

Co-authored-by: Kaity A <kaity@atikayda.au>

packages/backend/src/core/UserFollowingService.ts

@@ -511,6 +511,12 @@ export class UserFollowingService implements OnModuleInit {
 		if (blocking) throw new Error('blocking');
 		if (blocked) throw new Error('blocked');
 
+		// Remove old follow requests before creating a new one.
+		await this.followRequestsRepository.delete({
+			followeeId: followee.id,
+			followerId: follower.id,
+		});
+
 		const followRequest = await this.followRequestsRepository.insert({
 			id: this.idService.gen(),
 			followerId: follower.id,