docs(fix[pytest-plugin]): Remove stray fence before module directive

Author: tony

docs/pytest-plugin/index.md

@@ -12,8 +12,6 @@ your case, we won't stabilize APIs until we're sure everything is by the book.
 
 [connect with us]: https://github.com/tmux-python/libtmux/discussions
 
-```
-
 ```{module} libtmux.pytest_plugin
 :no-index:
 ```