Correct pyfakefs docs URL with language specifier (#611)

Looks like the documentation URL scheme for `pyfakefs` changed at some
point recently to include language specifier, which is causing link
checker to fail on existing URL.

Author: matt-graham

docs/pages/testing.md

@@ -19,7 +19,7 @@ layout: default
 | ---------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-----------------------------------------: |
 | [pytest-cov](https://pytest-cov.readthedocs.io/en/latest/index.html)   | A framework to generate coverage reports that plays nicely with `pytest`.                                                                                                                                                                                | <span class="label label-green">Best</span> |
 | [pytest-mock](https://pytest-mock.readthedocs.io/en/latest/index.html) | A framework to mock/patch objects that plays nicely with `pytest`.                                                                                                                                                                                       | <span class="label label-green">Best</span> |
-| [pyfakefs](https://pytest-pyfakefs.readthedocs.io/latest/)             | A plugin to create a full fake file system, for situations where you need something more complicated than the built in [`tmp_path` fixture](https://docs.pytest.org/en/stable/how-to/tmp_path.html#how-to-use-temporary-directories-and-files-in-tests). | <span class="label label-green">Best</span> |
+| [pyfakefs](https://pytest-pyfakefs.readthedocs.io/en/latest/)          | A plugin to create a full fake file system, for situations where you need something more complicated than the built in [`tmp_path` fixture](https://docs.pytest.org/en/stable/how-to/tmp_path.html#how-to-use-temporary-directories-and-files-in-tests). | <span class="label label-green">Best</span> |
 
 ## Property based testing