Task #8887: Added missing -y

Docker/lofar-base/Dockerfile.tmpl

@@ -43,7 +43,7 @@ RUN apt-get update && \
     apt-get install -y python-pip && \
     pip install numpy && \
     apt-get purge -y python-pip && \
-    apt-get autoremove && \
+    apt-get autoremove -y && \
     apt-get install -y nano
 
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