ci: Switched multiarch-java8 to be based on adoptopenjdk:8-jre-hotspot

Dockerfile

@@ -1,11 +1,10 @@
-FROM ubuntu:18.04
+FROM adoptopenjdk:8-jre-hotspot
 
 LABEL org.opencontainers.image.authors="Geoff Bourne <itzgeoff@gmail.com>"
 
 RUN apt-get update \
   && DEBIAN_FRONTEND=noninteractive \
   apt-get install -y \
-    openjdk-8-jre-headless \
     imagemagick \
     gosu \
     sudo \