Do not fail CI on Codecov upload errors

Update Codecov upload behavior in .github/workflows/testing-ci.yml to set fail_ci_if_error to false. This prevents the workflow from failing when the Codecov upload step encounters transient errors, ensuring CI jobs aren't blocked by Codecov availability or upload issues.

Author: C-Achard

.github/workflows/testing-ci.yml

@@ -77,4 +77,4 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           files: ./.coverage.py312.xml
-          fail_ci_if_error: true
+          fail_ci_if_error: false