terminology.rst: fix italics [skip-ci] (#6937)

- [x] Closes  #6932

@zmoon - obviously it would be nice if we had a linter for this but this is for another time.

Author: mathause

doc/user-guide/terminology.rst

@@ -5,8 +5,8 @@ Terminology
 ===========
 
 *Xarray terminology differs slightly from CF, mathematical conventions, and
-pandas; so we've put together a glossary of its terms. Here,* ``arr`` *
-refers to an xarray* :py:class:`DataArray` *in the examples. For more
+pandas; so we've put together a glossary of its terms. Here,* ``arr``
+*refers to an xarray* :py:class:`DataArray` *in the examples. For more
 complete examples, please consult the relevant documentation.*
 
 .. glossary::