[Chapel Merge] Add a delete to new test using unmanaged

Branch: refs/heads/main
Revision: ab1d90b
Author: mppf
Log Message:

Merge pull request #18388 from mppf/fix-leak-new-test

Add a delete to new test using unmanaged

Follow-up to PR #17248.

Adds a delete so that the test does not leak memory.

Trivial and not reviewed.

Modified Files:
M test/types/sync/ferguson/sync-unmanaged-nilable.chpl

Compare: https://github.com/chapel-lang/chapel/compare/5ae0f02d95c8...ab1d90b09716