Remove deprecated codecov dependency from CI (GenericMappingTools#1494)

The codecov python package is deprecated in favour of a bash script,
so it should be removed from PyGMT's CI dependency lists. For more
info, see codecov/codecov-python#325 and
https://about.codecov.io/blog/codecov-uploader-deprecation-plan.

* Refresh codecov badge to be the official one
* Drop deprecated codecov dependency from conda install
* Add note to maintenance.md on how code coverage reports are handled

.github/workflows/ci_tests.yaml

@@ -92,7 +92,7 @@ jobs:
           conda install gmt=6.2.0 numpy=${{ matrix.numpy-version }} \
                         pandas xarray netCDF4 packaging \
                         ${{ matrix.optional-packages }} \
-                        codecov coverage[toml] dvc ipython make \
+                        coverage[toml] dvc ipython make \
                         pytest-cov pytest-mpl pytest>=6.0 \
                         sphinx-gallery
 

README.rst

@@ -16,9 +16,9 @@ PyGMT
 .. image:: https://github.com/GenericMappingTools/pygmt/workflows/GMT%20Dev%20Tests/badge.svg
     :alt: GitHub Actions GMT Dev Tests status
     :target: https://github.com/GenericMappingTools/pygmt/actions/workflows/ci_tests_dev.yaml
-.. image:: https://img.shields.io/codecov/c/github/GenericMappingTools/pygmt/main.svg?style=flat-square
+.. image:: https://codecov.io/gh/GenericMappingTools/pygmt/branch/main/graph/badge.svg?token=78Fu4EWstx
     :alt: Test coverage status
-    :target: https://codecov.io/gh/GenericMappingTools/pygmt
+    :target: https://app.codecov.io/gh/GenericMappingTools/pygmt
 .. image:: https://img.shields.io/pypi/pyversions/pygmt.svg?style=flat-square
     :alt: Compatible Python versions.
     :target: https://pypi.python.org/pypi/pygmt

doc/maintenance.md

@@ -87,6 +87,11 @@ There are 11 configuration files located in `.github/workflows`:
      Python/NumPy versions
    - Latest Python/NumPy versions + optional packages (e.g. GeoPandas)
 
+   This workflow is also responsible for uploading test coverage reports stored
+   in `.coverage.xml` to https://app.codecov.io/gh/GenericMappingTools/pygmt
+   via the [Codecov GitHub Action](https://github.com/codecov/codecov-action).
+   More codecov related configurations are stored in `.github/codecov.yml`.
+
 3. `ci_docs.yml` (Build documentation on Linux/macOS/Windows)
 
    This is run on every commit to the *main* and Pull Request branches.

environment.yml

@@ -16,7 +16,6 @@ dependencies:
     # Development dependencies
     - black
     - blackdoc
-    - codecov
     - coverage[toml]
     - docformatter
     - dvc