Include private domains

[fupduck]

In issue 24 problems regarding private tlds were mentioned.

To fix this I now include them. I did not see a reason to not change this.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.50%. Comparing base (d01d568) to head (40fd0d7).

Files	Patch %	Lines
certbot_dns_hetzner/dns_hetzner.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
- Coverage   89.36%   87.50%   -1.87%     
==========================================
  Files           2        2              
  Lines          47       48       +1     
==========================================
  Hits           42       42              
- Misses          5        6       +1     

Flag	Coverage Δ
unittests	87.50% <0.00%> (-1.87%)	⬇️

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