Correcting the documenation to match the code

doc/introduction-to-mongo.tex

@@ -98,8 +98,8 @@ export MONGODB_DB=db_name
       \textbf{Variable} & \textbf{Default/Action}\\
       \hline
       \texttt{MONGODB\_SERVER} & \texttt{localhost} \\
-      \texttt{MONGODB\_USERNAME} & No authentication. \\
-      \texttt{MONGODB\_PASSWD} & No authentication. \\
+      \texttt{MONGODB\_USERNAME} & \texttt{root} \\
+      \texttt{MONGODB\_PASSWD} & \texttt{example} \\
       \texttt{MONGODB\_DB} & \texttt{test} \\ \hline
     \end{tabular}
   \end{center}