Update readme to remove mention of DockerHub registry

[rv0lt]

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1. Description / Summary

Remove mention of DockerHub registry

2. Jira task / GitHub issue

Link to the github issue or add the Jira task ID here.

3. Type of change

What type of change(s) does the PR contain?

Check the relevant boxes below. For an explanation of the different sections, enter edit mode of this PR description template.

• [] New feature
  • Breaking: Why / How? Add info here.
  • Non-breaking
• Database change: Remember the to include a new migration version, or explain here why it's not needed.
• Bug fix
• Security Alert fix
  • Package update
    • Major version update
• Documentation
• Workflow
• Tests only

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.52%. Comparing base (7f3414d) to head (83a2df4).
Report is 10 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1558   +/-   ##
=======================================
  Coverage   92.52%   92.52%           
=======================================
  Files          29       29           
  Lines        4868     4868           
=======================================
  Hits         4504     4504           
  Misses        364      364           

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[i-oden]

A couple minor changes in order to be extra clear.

[i-oden]

OK to merge!