test: add mustCall to test-dgram-implicit-bind.js

PR-URL: https://github.com/nodejs/node/pull/27452


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>