Fixed a typo in the documentation.

% The file loads the following packages:

% \begin{itemize}

%   \item\textsf{tikz} -- Used for dimension arithmetic.

%   \item\textsf{geometry} -- Used for the modifications of the type

%     area dimensions.

%   \item\textsf{changepage} -- Used for width adjustments.

% \end{itemize}

%    \begin{macrocode}

\thesis@require{tikz}