gzipping certain responses is known to cause problems with QR code logins.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3749

Gzipping at the synapse-reverse-proxy-companion level and not at the
level of the outer-most reverse-proxy (Traefik) also sounds non-ideal.

This change only affects setups powered by Synapse workers.

Non-worker setups (and setups powered by other homeservers) were not
having their requests go through synapse-reverse-proxy-companion anyway,
so this change does not affect them.

Future patches may enable response compression support at the Traefik level for
all setups.