Remove redundant qubes-dom0-update message

[alimirjamali]

Message for --check-only is moved to qubes-dom0-update main fix: https://github.com/QubesOS/qubes-core-admin-linux/pull/162 original issue: https://github.com/QubesOS/qubes-issues/issues/6126

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.57%. Comparing base (0f346ad) to head (d6510a9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #518   +/-   ##
=======================================
  Coverage   70.57%   70.57%           
=======================================
  Files           3        3           
  Lines         469      469           
=======================================
  Hits          331      331           
  Misses        138      138           

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