logging: Cut old logWarningToSentry.
logging: Cut old logWarningToSentry.

This has no callsites, so nothing else needs to be updated.

For places where we *should* be calling something like this, we'll use
the new `logging.warn` instead.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile