typo fix.

Doc/lib/libunittest.tex

@@ -51,7 +51,7 @@ indicate the results of executing the tests.
 
 The test case and test fixture concepts are supported through the
 \class{TestCase} and \class{FunctionTestCase} classes; the former
-should be used when creating new tests, and the later can be used when
+should be used when creating new tests, and the latter can be used when
 integrating existing test code with a PyUnit-driven framework.  When
 building test fixtures using \class{TestCase}, the \method{setUp()}
 and \method{tearDown()} methods can be overridden to provide