Fix Dockerfile

Building the workspace docker image with Dockerfile-71 failed because
of missing "&&"

workspace/Dockerfile-71

@@ -52,7 +52,7 @@ ENV PGID ${PGID}
 
 RUN groupadd -g ${PGID} laradock && \
     useradd -u ${PUID} -g laradock -m laradock && \
-    apt-get update -yqq \
+    apt-get update -yqq && \
     apt-get install -y python2.7
 
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