build(deps): bump codecov/codecov-action from 1 to 2.1.0 (#1647)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/tests.yml

@@ -85,7 +85,7 @@ jobs:
 
     - name: Upload to Codecov
       if: github.repository == 'executablebooks/jupyter-book'
-      uses: codecov/codecov-action@v1
+      uses: codecov/codecov-action@v2.1.0
       with:
         name: ebp-jupyter-book-pytests-py3.8
         flags: pytests