Remove an errant double link.

Thanks to TimonKnigge@

Change-Id: If5d77d9fe456991169ed70f12839af028755fc4f

docs/source/nnls_solving.rst

diff --git a/docs/source/nnls_solving.rst b/docs/source/nnls_solving.rst
index 285df3a..b3d0091 100644
--- a/docs/source/nnls_solving.rst
+++ b/docs/source/nnls_solving.rst
@@ -1377,7 +1377,7 @@
 
    An instance of the ordering object informs the solver about the
    desired order in which parameter blocks should be eliminated by the
-   linear solvers. See section~\ref{sec:ordering`` for more details.
+   linear solvers.
 
    If ``NULL``, the solver is free to choose an ordering that it
    thinks is best.