…rovider

The abstract `LogRecordProcessor.on_emit()` and `shutdown()` methods,
`ConcurrentMultiLogRecordProcessor.on_emit()` and `shutdown()`, and
`LoggerProvider.shutdown()` were missing `-> None` return type
annotations. This causes mypy `no-untyped-call` errors for callers
using strict type checking.

The sibling classes (`MultiLogRecordProcessor`, `TracerProvider`) already
have correct annotations — this aligns the logs module to match.