test: disable azure-arc-onboarding addon in everything cluster config

[jackfrancis]

Reason for Change:

This PR removes the azure-arc-onboarding addon from the "everything" test cluster config, because there is already a test cluster config dedicated to validating that addon.

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

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[codecov]

Codecov Report

Merging #3756 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3756   +/-   ##
=======================================
  Coverage   73.19%   73.19%           
=======================================
  Files         148      148           
  Lines       25367    25367           
=======================================
  Hits        18568    18568           
  Misses       5663     5663           
  Partials     1136     1136           

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