Removed DOSEMU, not avialable for arm

Dockerfile

@@ -23,14 +23,6 @@ RUN apt-get update \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
-# Other Utilities
-RUN echo "deb http://ftp.au.debian.org/debian/ stretch contrib" > /etc/apt/sources.list.d/contrib.list
-RUN apt-get update \
-    && apt-get install -yqq dosemu \
-    && apt-get -y autoremove \
-    && apt-get clean \
-    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
-
 # Build SBBS
 RUN apt-get update \
     && apt-get install -yqq build-essential libnspr4-dev libncurses5-dev libmozjs185-dev cvs wget pkgconf \