Fix codecov failure after multiple pushes made to PR

Refer to here for more details: https://github.com/diffpy/diffpy.fourigui/pull/58#issuecomment-2462566032. Codecov is failing after additional pushes are made to a PR. Here's a reference for potential fix: https://github.com/codecov/codecov-action/issues/1580. 
