[devman] fix ptests directive table layout

doc/developer/advance.tex

@@ -949,7 +949,7 @@ Figure~\ref{fig:test-directives} shows all the directives that can be used in
 the configuration header of a test (or a test suite).
 \begin{figure}[ht]
 \begin{center}
-\begin{tabular}{|c|c|p{5cm}|l|}
+\begin{tabular}{|c|c|p{5cm}|p{6cm}|}
 \hline
 \textbf{Kind} & \textbf{Name} & \textbf{Specification} & \textbf{default}\\
 \hline