Removed the `SYNAPSE_SMTP_*` docker container environment variables. Using these environment variables prevented the docker container from starting in Synapse v1.0, even though they didn't actually allow any functionality anyway. Users are advised to remove `SYNAPSE_SMTP_HOST`, `SYNAPSE_SMTP_PORT`, `SYNAPSE_SMTP_USER`, `SYNAPSE_SMTP_PASSWORD` and `SYNAPSE_SMTP_FROM` environment variables from their docker run commands.