replace RE2 with RegExp for regex word mute validation

packages/backend/src/server/api/endpoints/i/update.ts

@@ -3,7 +3,6 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import RE2 from 're2';
 import * as mfm from '@transfem-org/sfm-js';
 import { Inject, Injectable } from '@nestjs/common';
 import ms from 'ms';
@@ -325,7 +324,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 					if (!regexp) throw new ApiError(meta.errors.invalidRegexp);
 
 					try {
-						new RE2(regexp[1], regexp[2]);
+						new RegExp(regexp[1], regexp[2]);
 					} catch (err) {
 						throw new ApiError(meta.errors.invalidRegexp);
 					}