Update README.rst

Author: bckohan

README.rst

@@ -106,7 +106,7 @@ accessible as their enumeration type rather than by-value:**
 `enum-properties <https://pypi.org/project/enum-properties/>`_ which makes
 possible very rich enumeration fields.
 
-`pip install enum-properties`
+```pip install enum-properties```
 
 .. code:: python