DNS - correct rr type `0` to be in line with RFC

[wesinator]

Checklist:

• [x] If you are new to Scapy: I have checked CONTRIBUTING.md (esp. section submitting-pull-requests)
• [x] I squashed commits belonging together
• [x] I added unit tests or explained why they are not relevant
• [x] I executed the regression tests (using cd test && ./run_tests or tox)
• [x] If the PR is still not finished, please create a Draft Pull Request

set DNS rr type 0 label to "RESERVED", per latest IANA + RFC https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-4

see https://github.com/secdev/scapy/pull/4416#issuecomment-2166780436