replace String.random with randomstring

packages/import-qduoj/index.ts

@@ -4,7 +4,7 @@ import path from 'path';
 import { Readable } from 'stream';
 import {
     buildContent, Context, extractZip, FileTooLargeError, fs, Handler, PERM,
-    ProblemConfigFile, ProblemModel, Schema, ValidationError, yaml, Zip,
+    ProblemConfigFile, ProblemModel, randomstring, Schema, ValidationError, yaml, Zip,
 } from 'hydrooj';
 
 const tmpdir = path.join(os.tmpdir(), 'hydro', 'import-qduoj');
@@ -49,7 +49,7 @@ const ProblemSchema = Schema.object({
 class ImportQduojHandler extends Handler {
     async fromFile(domainId: string, zipfile: string) {
         const zip = new Zip.ZipReader(Readable.toWeb(fs.createReadStream(zipfile)));
-        const tmp = path.resolve(tmpdir, String.random(32));
+        const tmp = path.resolve(tmpdir, randomstring(32));
         await extractZip(zip, tmp, {
             strip: true,
             parseError: (e) => new ValidationError('zip', null, e.message),