Fix unenroll_by_email for multitenant email settings

[bryanlandia]

Change description

Make unenroll_by_email multitenant email aware Fix ENG-57

Type of change

• [x] Bug fix (fixes an issue)
• [ ] New feature (adds functionality)

Related issues

https://appsembler.atlassian.net/browse/ENG-57

Checklists

Development

• [x] Lint rules pass locally
• [x] Application changes have been tested thoroughly
• [x] Automated tests covering modified code pass

Security

• [x] Security impact of change has been considered
• [x] Code follows company security practices and guidelines

Code review

• [x] Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• [x] "Ready for review" label attached and reviewers assigned
• [ ] Changes have been reviewed by at least one other contributor
• [x] Pull request linked to task tracker where applicable

[github-actions[bot]]

Checking git merge conflicts against https://github.com/edx/edx-platform.git

Comparing with	open-release/nutmeg.master
Benchmark conflicts with main	293
Current conflicts	293
Summary	Good work! No added conflicts.

Comparing with	master
Benchmark conflicts with main	301
Current conflicts	301
Summary	Good work! No added conflicts.

[github-actions[bot]]

Checking git merge conflicts against https://github.com/edx/edx-platform.git

Comparing with	open-release/nutmeg.master
Benchmark conflicts with main	293
Current conflicts	293
Summary	Good work! No added conflicts.

Comparing with	master
Benchmark conflicts with main	301
Current conflicts	301
Summary	Good work! No added conflicts.

[github-actions[bot]]

Checking git merge conflicts against https://github.com/edx/edx-platform.git

Comparing with	open-release/nutmeg.master
Benchmark conflicts with main	296
Current conflicts	296
Summary	Good work! No added conflicts.

Comparing with	master
Benchmark conflicts with main	304
Current conflicts	304
Summary	Good work! No added conflicts.