Add a conditional check for if user is an admin for channel sharing

[marcellamaki]

Summary

Description of the change(s) you made

Updates the verifyChannel function to have an alternate condition for if a user is an admin (and thus should be able to share the channel, even if they don't have explicitly set editor permissions)

Manual verification steps performed

1. Created channel UserA
2. Signed in as admin [email protected]
3. Accessed this channel through admin panel under "Users" tabs
4. Shared channel - it now works!

Screenshots (if applicable)

admin-share.mp4

Does this introduce any tech-debt items?

I do not think so!

---

Reviewer guidance

How can a reviewer test these changes?

See manual verification above

References

Fixes #3258

Contributor's Checklist

PR process:

• If this is an important user-facing change, PR or related issue the CHANGELOG label been added to this PR. Note: items with this label will be added to the CHANGELOG at a later time
• If this includes an internal dependency change, a link to the diff is provided
• The docs label has been added if this introduces a change that needs to be updated in the user docs?
• If any Python requirements have changed, the updated requirements.txt files also included in this PR
• Opportunities for using Google Analytics here are noted
• Migrations are safe for a large db

Studio-specifc:

• All user-facing strings are translated properly
• The notranslate class been added to elements that shouldn't be translated by Google Chrome's automatic translation feature (e.g. icons, user-generated text)
• All UI components are LTR and RTL compliant
• Views are organized into pages, components, and layouts directories as described in the docs
• Users' storage used is recalculated properly on any changes to main tree files
• If there new ways this uses user data that needs to be factored into our Privacy Policy, it has been noted.

Testing:

• Code is clean and well-commented
• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Any new interactions have been added to the QA Sheet
• Critical and brittle code paths are covered by unit tests

---

Reviewer's Checklist

This section is for reviewers to fill out.

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md