Remove ensure_integration_enabled_async

[sentrivana]

Removing ensure_integration_enabled_async since there are some unresolved issues with it.

This should be ok to just remove (as opposed to deprecate) since it's only meant to be used internally.

Closes #2892

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
14851	1	14850	4376

View the top 1 failed tests by shortest run time

tests.test_transport test_transport_works[threads-False-gzip-None-True-close-True]

Stack Traces | 0.668s run time

tests/test_transport.py:175: in test_transport_works
    assert not err and not out
E   assert (not '--- Logging error ---\nTraceback (most recent call last):\n  File ".../hostedtoolcache/Python/3.6.15.../x64/lib/python3...lhandlers\n    return old_callhandlers(self, record)\nMessage: \'background worker got kill request\'\nArguments: ()\n')

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[szokeasaurusrex]

looks good