net: fix typo in dns client unix test
net: fix typo in dns client unix test

Fix a typo DNS name, it should be [onion.vegetables.com](http://onion.vegetables.com/)

Change-Id: I4122a2305b8f5e774a834651e70c75b54e9386bd
GitHub-Last-Rev: 9907897944275c5f8c54c79667cbb1ef474539de
GitHub-Pull-Request: golang/go#36270
Reviewed-on: https://go-review.googlesource.com/c/go/+/212410
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

CAFxX/go,golang/go,akutz/go,cloudflare/go,akutz/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,cloudflare/go,cloudflare/go,cloudflare/go,akutz/go,nawawi/go,akutz/go,nawawi/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,golang/go,akutz/go,golang/go,akutz/go,nawawi/go,akutz/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,akutz/go,golang/go,golang/go,golang/go