Log Message:
matrix-synapse: update to 1.37.1.

Synapse 1.37.1 (2021-06-30) ===========================

This release resolves issues (such as
[#9490](https://github.com/matrix-org/synapse/issues/9490)) where
one busy room could cause head-of-line blocking, starving Synapse
from processing events in other rooms, and causing all federated
traffic to fall behind. Synapse 1.37.1 processes inbound federation
traffic asynchronously, ensuring that one busy room won't impact
others. Please upgrade to Synapse 1.37.1 as soon as possible, in
order to increase resilience to other traffic spikes.

No significant changes since v1.37.1rc1.

Synapse 1.37.1rc1 (2021-06-29) ==============================

Features --------

- Handle inbound events from federation asynchronously.
([\#10269](https://github.com/matrix-org/synapse/issues/10269),
[\#10272](https://github.com/matrix-org/synapse/issues/10272))