Do not fail CI if Codecov upload fails

This works around codecov/codecov-action#37.

Author: adamtheturtle

.github/workflows/ci.yml

@@ -51,4 +51,4 @@ jobs:
       - name: "Upload coverage to Codecov"
         uses: "codecov/codecov-action@v1"
         with:
-          fail_ci_if_error: true
+          fail_ci_if_error: false