dgram: remove usage of public require('util')

Use `require('internal/util').deprecate` instead of
`require('util').deprecate`.

Refs: https://github.com/nodejs/node/issues/26546

PR-URL: https://github.com/nodejs/node/pull/26770


Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>