Fix Dispatch Queue Leak

[xiazhvera]

Issue #, if available:

Description of changes:
Release dispatch queue on event loop destroy.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.72%. Comparing base (a32bb73) to head (7b1bd2c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #750   +/-   ##
=======================================
  Coverage   78.72%   78.72%           
=======================================
  Files          30       30           
  Lines        6398     6398           
=======================================
  Hits         5037     5037           
  Misses       1361     1361           

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[sbSteveK]

Simple cleanup!