doc/doxygen/refman.tex: fix text

doc/doxygen/refman.tex

@@ -10,7 +10,7 @@
 ~\\
 \vspace*{15cm}
 \begin{flushright}
-Generated by Doxygen $doxygenversion on $datetime
+Generated by Doxygen.
 \end{flushright}
 \end{titlepage}