community/synapse: add secfix comment for CVE-2020-26890

Announcement: https://matrix.org/blog/2020/11/23/synapse-disclosing-cve-2020-26890
7 jobs for !14902 with synapse-secfix in 1 minute and 39 seconds
detached
Status Job ID Name Coverage
  Lint
failed #253491
docker-alpine x86_64 allowed to fail
lint

00:00:08

 
  Build
canceled #253496
docker-alpine ci-build aarch64
build-aarch64

canceled #253497
docker-alpine ci-build armv7
build-armv7

canceled #253495
docker-alpine ci-build ppc64le
build-ppc64le

canceled #253494
docker-alpine ci-build s390x
build-s390x

00:01:19

failed #253493
docker-alpine ci-build x86
build-x86

00:00:10

failed #253492
docker-alpine ci-build x86_64
build-x86_64

00:00:09

 
Name Stage Failure
failed
lint Lint
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failed
build-x86_64 Build
No job log
failed
build-x86 Build
No job log