Hide homeserver token from aiohttp logs

[pacien]

By default, the aiohttp logger is set to the INFO level, which causes all HTTP requests to be logged with the appservice's token in them. This might be a security issue.

For reference, Synapse redacts all tokens when logging requests.

[tulir]

Related to #321

[pacien]

An easy workaround could be to set this logger's level to WARNING by default instead.

https://github.com/tulir/mautrix-telegram/blob/281f7203dc6eec8be9e6489a8bf29ad7e850f07d/example-config.yaml#L345-L346

[tulir]

This should be fixed on the server side (matrix-org/matrix-spec-proposals#2832)