Update docs/roman/ramp_fitting/description.rst

Co-authored-by: Eddie Schlafly <[email protected]>

docs/roman/ramp_fitting/description.rst

@@ -229,7 +229,7 @@ resultants in the ramp, while double-difference refers to the difference between
 and a resultant two steps away (the resultant adjacent to a resultant adjacent to the resultant
 in question).
 
-To compute these statistics, we need the single-difference excess slope :math:`\delta_{i, i+1}` and
+To compute these statistics, the single-difference excess slope :math:`\delta_{i, i+1}` and
 the double-difference excess slope :math:`\delta_{i, i+2}` are computed as:
 
 .. math::