Fix deprecation warning

WARNING: 'conda clean --source-cache' is deprecated.

PythonServer/Dockerfile

@@ -11,7 +11,7 @@ RUN conda update -n base conda \
   && conda config --system --set channel_alias https://artifactory.esss.lu.se/artifactory/api/conda \
   && conda config --system --set use_only_tar_bz2 true \
   && conda env create -n pos -f /app/environment.yml \
-  && conda clean -tipsy
+  && conda clean -ay
 
 COPY --chown=csi:csi pos-python-server.py /app/
 # Make sure the /app directory is owned by csi