Fix typo (from SF bug #1086127).

Doc/lib/libos.tex

@@ -1820,7 +1820,7 @@ Also available via \module{os.path}.
 
 \begin{datadesc}{pathsep}
 The character conventionally used by the operating system to separate
-search patch components (as in \envvar{PATH}), such as \character{:} for
+search path components (as in \envvar{PATH}), such as \character{:} for
 \POSIX{} or \character{;} for Windows.
 Also available via \module{os.path}.
 \end{datadesc}