Revert specifying pandas version and clean up installation for 37 recipe

containers/Dockerfile-test-suite-python37

@@ -20,15 +20,18 @@ ln -s /opt/conda/etc/profile.d/conda.sh /etc/profile.d/conda.sh && \
 echo ". /opt/conda/etc/profile.d/conda.sh" >> ~/.bashrc && \
 echo "conda activate base" >> ~/.bashrc
 
+# Update pip and setuptools
+RUN pip install --upgrade pip \
+&& LC_ALL=C pip install --upgrade setuptools
+
 # Install conda-installable programs
-RUN conda install -y numpy scipy matplotlib pandas==0.23
+RUN conda install -y numpy scipy matplotlib pandas
 
+# Install conda-forge-installable programs
 RUN conda install -c conda-forge deepdish
 
 # Install requirements
-RUN pip install --upgrade pip \
-&& pip install --upgrade setuptools \
-&& pip install future \
+RUN pip install future \
 pycondor>=0.5 \
 configargparse \
 flake8 \