Fix(backend): Limit antenna/webhook/list to exact amount (#14036)

... not +1
* Update antennas/clips e2e test

packages/backend/test/e2e/antennas.ts

@@ -163,8 +163,7 @@ describe('アンテナ', () => {
 	});
 
 	test('が上限いっぱいまで作成できること', async () => {
-		// antennaLimit + 1まで作れるのがキモ
-		const response = await Promise.all([...Array(DEFAULT_POLICIES.antennaLimit + 1)].map(() => successfulApiCall({
+		const response = await Promise.all([...Array(DEFAULT_POLICIES.antennaLimit)].map(() => successfulApiCall({
 			endpoint: 'antennas/create',
 			parameters: { ...defaultParam },
 			user: alice,