Resolve suppressed Coroutines related `DEPRECATION` warning for `ReviewModerationHandlerTests`

[ParaskP7]

As part of #6902 and this commit, the ReviewModerationHandlerTests test and all its warnings got suppressed with DEPRECATION.

The warnings occur because this ReviewModerationHandlerTests test suite is the only such suite that still uses the old way of testing with Coroutines. As part of the Coroutine 1.6 PR, migrating this test suite to the new way didn't happen as different approaches using both 'Standard' and 'Unconfined' dispatchers didn't work, 3 tests were always failing. One would need to remove this figure out how to use the new way of testing Coroutines on this ReviewModerationHandlerTests, maybe even rewriting it if need be.

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