ref: test deprecated warnings raised by legacy conversion

[asottile-sentry]

part of an effort to make tests warnings-clean

previously this was crashing with errors:

__________________________ test_apply_legacy_settings __________________________
tests/sentry/runner/test_initializer.py:182: in test_apply_legacy_settings
    apply_legacy_settings(settings)
src/sentry/runner/initializer.py:529: in apply_legacy_settings
    warnings.warn(
src/sentry/utils/warnings.py:59: in warn
    handler(warning, **kwargs)
src/sentry/utils/warnings.py:92: in <lambda>
    lambda warning, stacklevel=1: warnings.warn(warning, stacklevel=stacklevel + 2),
E   sentry.utils.warnings.DeprecatedSettingWarning: The SENTRY_USE_QUEUE setting is deprecated. Please use CELERY_ALWAYS_EAGER instead. See