SSB-47: escaping newlines

CAL/Docker/HolographyBase/Dockerfile

@@ -100,9 +100,9 @@ COPY --from=base-build /opt/python-casacore/ /opt/python-casacore/
 COPY --from=base-build /opt/dysco/ /opt/dysco/
 
 ## Installing convenience packages
-RUN apt install -y
-    ipython3
-    less
-    most
-    mc
+RUN apt install -y \
+    ipython3 \
+    less \
+    most \
+    mc \
     vim