Typo fix.

Doc/lib/libunittest.tex

@@ -540,7 +540,7 @@ easier.}
 
 \begin{funcdesc}{main}{\optional{module\optional{,
                  defaultTest\optional{, argv\optional{,
-                 testRunner\optional{, testRunner}}}}}}
+                 testRunner\optional{, testLoader}}}}}}
   A command-line program that runs a set of tests; this is primarily
   for making test modules conveniently executable.  The simplest use
   for this function is to include the following line at the end of a