Bump crossbario/crossbar in /docker/crossbar

Bumps crossbario/crossbar from cpy3-20.8.1 to cpy3-20.12.1.

---
updated-dependencies:
- dependency-name: crossbario/crossbar
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

docker/crossbar/Dockerfile

@@ -3,7 +3,7 @@
 # https://crossbar.io/docs/Creating-Docker-Images/
 
 # Use ocs base image
-FROM crossbario/crossbar:cpy3-20.8.1
+FROM crossbario/crossbar:cpy3-20.12.1
 
 # Run as root to put config in place and chown
 USER root