codecov-action: explicitly set fail_ci_if_error: true (instead of relying on the default value)

Author: DilumAluthge

.github/workflows/UnitTests.yml

@@ -76,6 +76,7 @@ jobs:
     - uses: codecov/codecov-action@v5
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
+        fail_ci_if_error: false
         files: lcov.info
     - uses: julia-actions/julia-uploadcoveralls@v1
       continue-on-error: true