Add missing \

Add a missing \ that I must somehow forgotten to add or accidentally removed.

docker-compose/itango/Dockerfile

@@ -11,5 +11,5 @@ RUN sudo apt-get -y update && \
     sudo aptitude autoclean
 
 COPY lofar-requirements.txt /lofar-requirements.txt
-RUN sudo pip3 install -r /lofar-requirements.txt &&
+RUN sudo pip3 install -r /lofar-requirements.txt && \
     sudo pip3 cache purge