asyncio doc: fix typo in an example

--HG--
branch : 3.4
Merge 3.4 (asyncio doc)
Issue #22676: Make the pickling of global objects which don't have a __module__ attribute less slow.
Issue #13918: Provide a locale.delocalize() function which can remove
locale-specific number formatting from a string representing a number,
without then converting it to a specific type.  Patch by Cédric Krier.
Fix markup and spacing.