fix: add unittest patch back to special exams tests

[wgu-taylor-payne]

Description

Adds back import that existed while #38874 was developed, but was removed before that PR was merged.

Supporting information

PR: #38874
Failure on master: https://github.com/openedx/openedx-platform/actions/runs/29773720214/job/88457960448

Testing instructions

Run ruff checks and see that there are no issues reported.

Deadline

ASAP

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[Anas12091101]

LGTM