Update StandardNamesRules.rst

Suggestion from Jesse

Co-authored-by: Jesse Nusbaumer <nusbaume@ucar.edu>

StandardNamesRules.rst

@@ -38,8 +38,8 @@ CCPP Standard Name Rules
    `CF guidelines <http://cfconventions.org/Data/cf-standard-names/docs/guidelines.html>`_),
    but have since evolved for better consistency and generality across a broader set of fields
    than was originally envisioned by the CF conventions. "``medium``" should be specified when
-   the variable in question is a substance or other quantity contained within some other the medium
-   (e.g. for with air as the medium, mole_fraction_of_ozone_in_air, the base name is ozone, while the medium is air). 
+   the variable in question is a substance or other quantity contained within some other medium
+   (e.g. for "mole_fraction_of_ozone_in_air", the base name is "ozone", while the medium is "air"). 
    "Transformation" refers to descriptors such as "``tendency_of``", "``log10``", or other operations or processes describing some transformation or adjustment of a variable; a detailed list of possible transformations can be found `later in this document <#transformations>`_.
    Other parts of the construction provide information about a variable's horizontal surface
    (e.g. ``at_cloud_base``), component (i.e. direction of variable, e.g. ``downward``), process (e.g.