Drop all references to codecov

Upstream yanked all existing releases from PyPI as a way to signal
deprecation of their library, breaking all pipelines that rely on them.

This isn't the first time they've broken all pipelines as a result on
having no idea of how CI downstream systems work, so let's just stay
away from them.

.github/workflows/tests.yml

@@ -16,10 +16,7 @@ jobs:
         with:
           python-version: ${{ matrix.python }}
           architecture: x64
-      - run: pip install tox codecov
+      - run: pip install tox
       - run: tox
         env:
           TOXENV: django${{ matrix.django }}
-      - run: codecov
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

README.rst

@@ -5,10 +5,6 @@ django-renderpdf
   :target: https://github.com/WhyNotHugo/django-renderpdf/actions/workflows/tests.yml
   :alt: Actions Status
 
-.. image:: https://codecov.io/gh/WhyNotHugo/django-renderpdf/branch/main/graph/badge.svg
-  :target: https://codecov.io/gh/WhyNotHugo/django-renderpdf
-  :alt: Codecov coverage report
-
 .. image:: https://img.shields.io/pypi/v/django-renderpdf.svg
   :target: https://pypi.python.org/pypi/django-renderpdf
   :alt: Version on PyPI