Fix a minor typographical error in the version history.

Change-Id: I9648aaf218321f9e144de20ef5e512385a6cfe34

docs/source/version_history.rst

diff --git a/docs/source/version_history.rst b/docs/source/version_history.rst
index 84f8194..82aed8b 100644
--- a/docs/source/version_history.rst
+++ b/docs/source/version_history.rst
@@ -14,7 +14,7 @@
 #. Auto-differentiable implementations of Bessel functions, ``floor``,
    and ``ceil`` (Alessandro Gentilini & Michael Vitus)
 #. New 2D and 3D SLAM examples. (Michael Vitus)
-#. Added``EigenQuaternionParameterization``. (Michael Vitus)
+#. Added ``EigenQuaternionParameterization``. (Michael Vitus)
 #. Added ``Problem::IsParameterBlockConstant`` (Thomas Schneider)
 #. A complete refactoring of ``TrustRegionMinimizer``. (Sameer Agarwal)
 #. Gradient checking cleanup and local parameterization bugfix (David