Fix missing private channels in import workflow

[jonboiser]

Summary

Fixes #3926

Reviewer guidance

1. Re-do scenario in Imported channel not showing at the channel list. #3926.

References

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Contributor Checklist

• Contributor has fully tested the PR manually
• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If there are any front-end changes, before/after screenshots are included
• If this is an important user-facing change, PR or related issue has a 'changelog' label

Reviewer Checklist

• Automated test coverage is satisfactory
• Reviewer has fully tested the PR manually
• PR has been tested for accessibility regressions
• External dependencies files were updated (yarn and pip)
• Documentation is updated
• Link to diff of internal dependency change is included
• CHANGELOG.rst is updated for high-level changes
• Contributor is in AUTHORS.rst

[codecov]

Codecov Report

Merging #3929 into release-v0.10.x will not change coverage.
The diff coverage is n/a.

@@               Coverage Diff                @@
##           release-v0.10.x    #3929   +/-   ##
================================================
  Coverage            77.61%   77.61%           
================================================
  Files                  217      217           
  Lines                 9309     9309           
  Branches              1173     1173           
================================================
  Hits                  7225     7225           
  Misses                1830     1830           
  Partials               254      254

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[indirectlylit]

I wasn't actually able to reproduce the original issue but was still able to import after testing