backend: Fix import of sanitize-html

I'm not sure how it managed to work so far, but the function is the default
export, using the namespace like a function should not have worked,
maybe something under the hood was correcting it back

packages/backend/src/server/api/endpoints/users/report-abuse.ts

@@ -1,4 +1,4 @@
-import * as sanitizeHtml from 'sanitize-html';
+import sanitizeHtml from 'sanitize-html';
 import config from '@/config/index.js';
 import { publishAdminStream } from '@/services/stream.js';
 import { AbuseUserReports, Users } from '@/models/index.js';