Remove the pin to a specific java version below 8. (#236)

docker/Dockerfile

@@ -78,13 +78,6 @@ RUN { \
 RUN ln -svT "/usr/lib/jvm/java-8-openjdk-$(dpkg --print-architecture)" /docker-java-home
 ENV JAVA_HOME /docker-java-home
 
-ENV JAVA_VERSION 8u181
-ENV JAVA_DEBIAN_VERSION 8u181-b13-2~deb9u1
-
-# see https://bugs.debian.org/775775
-# and https://github.com/docker-library/java/issues/19#issuecomment-70546872
-ENV CA_CERTIFICATES_JAVA_VERSION 20170531+nmu1
-
 RUN set -ex; \
 	\
 # deal with slim variants not having man page directories (which causes "update-alternatives" to fail)
@@ -94,8 +87,8 @@ RUN set -ex; \
 	\
 	apt-get update; \
 	apt-get install -y --no-install-recommends \
-		openjdk-8-jdk="$JAVA_DEBIAN_VERSION" \
-		ca-certificates-java="$CA_CERTIFICATES_JAVA_VERSION" \
+		openjdk-8-jdk \
+		ca-certificates-java \
 	; \
 	rm -rf /var/lib/apt/lists/*; \
 	\