Update changes.tex for 1.2.2

Change-Id: I8ed7e01374e2d5de54b7f9d25bfd7a5aa2da9a38

docs/changes.tex

@@ -1,6 +1,13 @@
 %!TEX root = ceres-solver.tex
 
 \chapter{Version History}
+\section*{1.2.2}
+\subsection{Bug Fixes}
+\begin{itemize}
+\item Fix constant parameter blocks, and other minor fixes (Thanks Markus Moll)
+\item Fix alignment issues when combining Jet and FixedArray in autodiff.
+\item Remove obsolete \texttt{build\_defs} file
+\end{itemize}
 \section*{1.2.1}
 \subsection{New Features}
 \begin{itemize}