Fix typo in traceback docs

Doc/library/traceback.rst

@@ -274,7 +274,7 @@ Module-Level Functions
 :class:`!TracebackException` objects are created from actual exceptions to
 capture data for later printing.  They offer a more lightweight method of
 storing this information by avoiding holding references to
-:ref:`traceback<traceback-objects>` and :ref:`frame<frame-objects>` objects
+:ref:`traceback<traceback-objects>` and :ref:`frame<frame-objects>` objects.
 In addition, they expose more options to configure the output compared to
 the module-level functions described above.