dockerfile fix and improved cleanup

Author: GoodforGod

Dockerfile

@@ -55,7 +55,6 @@ RUN cd /tmp \
 	$JAVA_HOME/lib/oblique-fonts \
 	$JAVA_HOME/plugin \
 	$JAVA_HOME/bin/jjs \
-    && apt-get upgrade -y \
     && apt-get remove -y wget \
     && apt-get clean -y \
     && apt-get autoremove -y \

README.md

@@ -1,5 +1,5 @@
 # Docker Debian Oracle JRE 10
-Docker Debian Slim image with cleaned Oracle JRE 10 Update 1 (size 253MB)
+Docker Debian Slim image with cleaned Oracle JRE 10 Update 1 (size 252MB)
 
 You must accept the [Oracle Binary Code License Agreement for Java SE](http://www.oracle.com/technetwork/java/javase/terms/license/index.html) to use this image.