Fix esmpy install instructions

Author: davidhassell

docs/source/installation.rst

@@ -108,7 +108,7 @@ visualisation package <http://ajheaps.github.io/cf-plot>`_, run:
    :caption: *Install with conda.*
 
    $ conda install -c conda-forge cf-python cf-plot udunits2
-   $ conda install -c conda-forge esmpy>=8.0.0
+   $ conda install -c conda-forge "esmpy>=8.0.0"
 
 The second of the two ``conda`` commands is required for
 :ref:`regridding <Regridding>` to work.
@@ -251,7 +251,7 @@ environments for which these features are not required.
 
   .. code-block:: console
 
-     $ conda install -c conda-forge esmpy>=8.0.0
+     $ conda install -c conda-forge "esmpy>=8.0.0"
 
   or may be installed from source.