MAINT: enable CODECOV_TOKEN for codecov action (#3573)

* MAINT: Bump codecov/codecov-action from 3 to 4

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3 to 4.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v3...v4)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

* Apply suggestions from code review

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Roberto Pastor Muela <[email protected]>
Co-authored-by: Massimo Capodiferro <[email protected]>

.github/workflows/unit_test_prerelease.yml

@@ -74,6 +74,8 @@ jobs:
           pytest --tx 6*popen --durations=50 --dist loadfile -v --cov=pyaedt  --cov-report=xml --junitxml=junit/test-results.xml --cov-report=html _unittest
 
       - uses: codecov/codecov-action@v3
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         if: matrix.python-version == '3.8'
         name: 'Upload coverage to Codecov'
 

.github/workflows/unit_tests.yml

@@ -73,6 +73,8 @@ jobs:
           pytest --durations=50 -v --cov=pyaedt --cov-report=xml --cov-report=html --junitxml=junit/test-results.xml _unittest_solvers
 
       - uses: codecov/codecov-action@v3
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
           name: 'Upload coverage to Codecov'
 
@@ -130,6 +132,8 @@ jobs:
           pytest -n 6 --dist loadfile --durations=50 -v --cov=pyaedt --cov-report=xml --cov-report=html --junitxml=junit/test-results.xml _unittest
 
       - uses: codecov/codecov-action@v3
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
           name: 'Upload coverage to Codecov'