Fix readme

Author: asvetlov

README.rst

@@ -260,7 +260,7 @@ Changelog
 0.18.0 (Unreleased)
 ~~~~~~~~~~~~~~~~~~~
 
-- Raise a warning if @pytest.mark.asyncio is applied to non-async function. `#275 <https://github.com/pytest-dev/pytest-asyncio/issues/275`_
+- Raise a warning if @pytest.mark.asyncio is applied to non-async function. `#275 <https://github.com/pytest-dev/pytest-asyncio/issues/275>`_
 
 0.17.2 (22-01-17)
 ~~~~~~~~~~~~~~~~~~~