Remove broken codecov integration (see mpmath/mpmath#709)

.github/workflows/coverage.yml

@@ -43,8 +43,3 @@ jobs:
           path: |
             coverage.xml
             build/coverage/html/
-      - name: Upload coverage data
-        uses: codecov/codecov-action@v4
-        with:
-          files: ./coverage.xml
-          fail_ci_if_error: false

README.rst

@@ -7,8 +7,6 @@ mpmath
    :target: https://pypi.python.org/pypi/mpmath
 .. |Build status| image:: https://github.com/mpmath/mpmath/workflows/test/badge.svg
    :target: https://github.com/mpmath/mpmath/actions?workflow=test
-.. |Code coverage status| image:: https://codecov.io/gh/mpmath/mpmath/branch/master/graph/badge.svg
-   :target: https://codecov.io/gh/mpmath/mpmath
 .. |Zenodo Badge| image:: https://zenodo.org/badge/2934512.svg
    :target: https://zenodo.org/badge/latestdoi/2934512