Use single backticks to create links

.. so that the reader of the documentation can readily get to the `traceback.print_exception` docs

Author: jepler

docs/library/sys.rst

@@ -24,7 +24,7 @@ Functions
       :class: attention
 
       This is simplified version of a function which appears in the
-      ``traceback`` module in CPython. Unlike ``traceback.print_exception()``,
+      `traceback` module in CPython. Unlike `traceback.print_exception()`,
       this function takes just exception value instead of exception type,
       exception value, and traceback object; *file* argument should be
       positional; further arguments are not supported.