Remove useless final echo

Dockerfile.alpine

@@ -15,8 +15,7 @@ RUN echo "@testing http://dl-cdn.alpinelinux.org/alpine/edge/testing" >> /etc/ap
     && rm -rf /tmp/* /var/tmp/* \
     && groupmod -g 1000 users \
     && useradd -u 911 -U -d /config -s /bin/false abc \
-    && usermod -G users abc \
-    && echo done
+    && usermod -G users abc
 
 ADD openvpn/ /etc/openvpn/
 ADD transmission/ /etc/transmission/