env variable name mistake

[Yaojia Lyu]

In this table:
https://github.com/slafs/sentry-docker/blob/master/README.md#available-environment-variables

SENTRY_USE_REDIS_BUFFER should be SENTRY_USE_REDIS_BUFFERS, according to the config file (https://github.com/slafs/sentry-docker/blob/master/sentry_docker_conf.py#L80).

thanks

[Sławomir Ehlert]

Thanks. You wanna make a PR?

[Yaojia Lyu]

Aha, just one character, no need to make a PR, thanks.

[Taylor Dolezal]

@slafs This issue can be closed

[Sławomir Ehlert]

thx