changed `-tipsy` flag to `--all -y`

Following the discussion in issue #861, this changes the `conda clean`
flags.

base-notebook/Dockerfile

@@ -79,7 +79,7 @@ RUN cd /tmp && \
     $CONDA_DIR/bin/conda config --system --set show_channel_urls true && \
     $CONDA_DIR/bin/conda install --quiet --yes conda="${CONDA_VERSION%.*}.*" && \
     $CONDA_DIR/bin/conda update --all --quiet --yes && \
-    conda clean -tipsy && \
+    conda clean --all -y && \
     rm -rf /home/$NB_USER/.cache/yarn && \
     fix-permissions $CONDA_DIR && \
     fix-permissions /home/$NB_USER
@@ -87,7 +87,7 @@ RUN cd /tmp && \
 # Install Tini
 RUN conda install --quiet --yes 'tini=0.18.0' && \
     conda list tini | grep tini | tr -s ' ' | cut -d ' ' -f 1,2 >> $CONDA_DIR/conda-meta/pinned && \
-    conda clean -tipsy && \
+    conda clean --all -y && \
     fix-permissions $CONDA_DIR && \
     fix-permissions /home/$NB_USER
 
@@ -101,7 +101,7 @@ RUN conda install --quiet --yes \
     'notebook=5.7.8' \
     'jupyterhub=0.9.6' \
     'jupyterlab=0.35.4' && \
-    conda clean -tipsy && \
+    conda clean --all -y && \
     jupyter labextension install @jupyterlab/hub-extension@^0.12.0 && \
     npm cache clean --force && \
     jupyter notebook --generate-config && \