The jenkins/jenkins:jdk11 Docker image is running Debian unstable ("sid") instead of Debian stable ("stretch"). Debian unstable is not intended for production use. Debian stable is intended for production use.
The most surprising is that the openjdk:11-jdk Docker image that is the base of the jenkins/jenkins:jdk11 Docker image is currently Debian stable. It surprises me that the base image is Debian stable while the derived image jenkins/jenkins:jdk11 is Debian unstable.
I assume some form of caching in the Docker image construction, or some other issue that is causing Debian unstable to be used instead of Debian stable.