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.

Author: WhyNotHugo

.github/workflows/tests.yml

@@ -25,12 +25,8 @@ jobs:
         with:
           python-version: ${{ matrix.python }}
       - name: Install test dependency
-        run: pip install tox codecov
+        run: pip install tox
       - name: Run tests
         run: tox
         env:
           TOXENV: ${{ matrix.variant }}
-      - name: Report coverage
-        run: codecov
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

README.rst

@@ -5,10 +5,6 @@ python-barcode
   :target: https://github.com/WhyNotHugo/python-barcode/actions
   :alt: CI status
 
-.. image:: https://codecov.io/gh/WhyNotHugo/python-barcode/branch/main/graph/badge.svg
-  :target: https://codecov.io/gh/WhyNotHugo/python-barcode
-  :alt: Build coverage
-
 .. image:: https://readthedocs.org/projects/python-barcode/badge/
   :target: https://python-barcode.rtfd.org/
   :alt: documentation