Update dns.rb

[briner]

type is depreceted and not anymore on the fields describe in the documentation

[purbon]

@briner thanks a lot for your contribution, before moving forward it will be necessary that you sign the CLA, you can see more info at https://www.elastic.co/contributor-agreement . Keep in mind to use the same email as the one used in your PR, this helps our do the necessary checks.

[briner]

the CLA is signed.

[elasticsearch-release]

Jenkins standing by to test this. If you aren't a maintainer, you can ignore this comment. Someone with commit access, please review this and clear it for Jenkins to run; then say 'jenkins, test it'.

[guyboertje]

LGTM