Fix typo in docs: max_lbfs_rank -> max_lbfgs_rank.

Change-Id: I49ffec85c2b43fe4f51fd214f461c2ec51360270

docs/source/nnls_solving.rst

diff --git a/docs/source/nnls_solving.rst b/docs/source/nnls_solving.rst
index 18d7aec..5863ff0 100644
--- a/docs/source/nnls_solving.rst
+++ b/docs/source/nnls_solving.rst
@@ -867,7 +867,7 @@
    Choices are ``FLETCHER_REEVES``, ``POLAK_RIBIERE`` and
    ``HESTENES_STIEFEL``.
 
-.. member:: int Solver::Options::max_lbfs_rank
+.. member:: int Solver::Options::max_lbfgs_rank
 
    Default: 20