Remove erroneous period.

Doc/lib/libunittest.tex

@@ -298,7 +298,7 @@ separate module, such as \file{widgettests.py}:
 \begin{itemize}
   \item The test module can be run standalone from the command line.
   \item The test code can more easily be separated from shipped code.
-  \item There is less temptation to change test code to fit the code.
+  \item There is less temptation to change test code to fit the code
         it tests without a good reason.
   \item Test code should be modified much less frequently than the
         code it tests.