Fix a small typo in solving.rst

Change-Id: Ib0b19d329a64230629b16e71437cdb53f10e551d

docs/source/solving.rst

diff --git a/docs/source/solving.rst b/docs/source/solving.rst
index e8dfd9f..fcc3c4c 100644
--- a/docs/source/solving.rst
+++ b/docs/source/solving.rst
@@ -1116,8 +1116,8 @@
 
    where :math:`\|\cdot\|_\infty` refers to the max norm, :math:`\Pi`
    is projection onto the bounds constraints and :math:`\boxplus` is
-   Plus operation that for the overall local parameterization
-   associated with the parameter vector.
+   Plus operation for the overall local parameterization associated
+   with the parameter vector.
 
 .. member:: double Solver::Options::parameter_tolerance