Switch to paths_ignore

[samtstern]

See #186
See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#onpushpull_requestpaths

When all the path names match patterns in paths-ignore, the workflow will not run. GitHub evaluates patterns defined in paths-ignore against the path name. A workflow with the following path filter will only run on push events that include at least one file outside the docs directory at the root of the repository.