Use SyslogIdentifier to improve logging

Reasoning is the same as for matrix-org/synapse#5023.

For us, the journal used to contain `docker` for all services, which
is not very helpful when looking at them all together (`journalctl -f`).

roles/matrix-synapse/templates/ext/mautrix-telegram/systemd/matrix-mautrix-telegram.service.j2

@@ -17,6 +17,7 @@ ExecStartPre=/usr/bin/docker run --rm --name matrix-mautrix-telegram-db \
 			-v {{ matrix_mautrix_telegram_base_path }}:/data:z \
 			{{ matrix_mautrix_telegram_docker_image }} \
 			alembic -x config=/data/config.yaml upgrade head
+
 ExecStart=/usr/bin/docker run --rm --name matrix-mautrix-telegram \
 			--log-driver=none \
 			--user={{ matrix_user_uid }}:{{ matrix_user_gid }} \
@@ -28,10 +29,12 @@ ExecStart=/usr/bin/docker run --rm --name matrix-mautrix-telegram \
 			-v {{ matrix_mautrix_telegram_base_path }}:/data:z \
 			{{ matrix_mautrix_telegram_docker_image }} \
 			python3 -m mautrix_telegram -c /data/config.yaml
+
 ExecStop=-/usr/bin/docker kill matrix-mautrix-telegram
 ExecStop=-/usr/bin/docker rm matrix-mautrix-telegram
 Restart=always
 RestartSec=30
+SyslogIdentifier=matrix-mautrix-telegram
 
 [Install]
 WantedBy=multi-user.target