Link to admin thesis URL in registrar import email

[jazairi]

Why these changes are being introduced:

The registar import email currently links to the
thesis URL for theses that have related held
theses. It would be more useful for processors
to link directly to the admin UI.

Relevant ticket(s):

• ETD-689

How this addresses that need:

This updates the links to use the admin URLs.

Side effects of this change:

None

Developer

• All new ENV is documented in README
• All new ENV has been added to Heroku Pipeline, Staging and Prod
• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)
• Stakeholder approval has been confirmed (or is not needed)

Code Reviewer

• The commit message is clear and follows our guidelines
  (not just this pull request message)
• There are appropriate tests covering any new functionality
• The documentation has been updated or is unnecessary
• The changes have been verified
• New dependencies are appropriate or there were no changes

Requires database migrations?

YES | NO

Includes new or updated dependencies?

YES | NO

[coveralls]

coverage: 98.25%. remained the same — etd-689 into main