Dynamic config generation based on environment variables in Synapse is
no longer supported. To pass secrets to container we use a patch that
implements configuration overrides via environment variables directly.
(to be upstreamed...)
Due to Synapse update, appservice configuration ConfigMaps don't need to
be copied into Synapse /data volume anymore.
Change-Id: I70e6480983bfb997362739c6ce0ec3c313320836