Annotate Psr\Log\LoggerInterface as provided by LogServiceProvider.

The Psr\Log\LoggerInterface was added to app->bind but not added to the
provides array in the LogServiceProvider.

See: https://github.com/itsgoingd/clockwork/issues/67
Merge pull request #5965 from spencerdeinum/add_psr_logger_log_service_provider

[4.2] Annotate Psr\Log\LoggerInterface as provided by LogServiceProvider.