Minor wording fix in docs

* Add "the distances" before the math expression in first paragraph

package/MDAnalysis/analysis/atomicdistances.py

@@ -34,6 +34,7 @@
 This module provides a class to efficiently compute distances between
 two groups of atoms with an equal number of atoms over a trajectory.
 Specifically, for two atom groups ``ag1`` and ``ag2``, it will return
+the distances
 
 .. math::
     |ag1[i] - ag2[i]|