community/synapse: add missing dependencies, re-enable

fixes #11873
7 jobs for !11652 with synapse in 24 minutes and 30 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed #190918
docker-alpine x86_64
lint

00:00:25

 
  Build
passed #190923
docker-alpine ci-build aarch64
build-aarch64

00:23:06

passed #190924
docker-alpine ci-build armv7
build-armv7

00:19:46

passed #190922
docker-alpine ci-build ppc64le
build-ppc64le

00:24:04

passed #190921
docker-alpine ci-build s390x
build-s390x

00:00:30

passed #190920
docker-alpine ci-build x86
build-x86

00:14:09

passed #190919
docker-alpine ci-build x86_64
build-x86_64

00:10:24