Remove landscape badge from README

The site is having difficulties, and the badge has seemed unreliable of late.
There is not currently a shields.io version we could use either,
badges/shields#493

Author: peterjc

README.rst

@@ -13,9 +13,6 @@ flake8-rst-docstrings
 .. image:: https://img.shields.io/pypi/dm/flake8-rst-docstrings.svg
    :alt: PyPI downloads
    :target: https://pypistats.org/packages/flake8-rst-docstrings
-.. image:: https://landscape.io/github/peterjc/flake8-rst-docstrings/master/landscape.svg?style=flat
-   :alt: Landscape Code Metrics
-   :target: https://landscape.io/github/peterjc/flake8-rst-docstrings/
 .. image:: https://img.shields.io/badge/code%20style-black-000000.svg
    :alt: Code style: black
    :target: https://github.com/ambv/black