ci: Always run the modified-plugin actions, don't use paths filter (#…

…131)

- Checks skipped with the "paths" filter never run, but we want to have
branch protection based on the `test-python` and `test-js` steps
- GitHub recommends not filtering on paths for required actions:
https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
- Don't filter on paths for triggering the action; each step is already
conditional on if there were actually changes to the package or not

.github/workflows/modified-plugin.yml

@@ -3,12 +3,6 @@ name: Test Modified Plugin
 on:
   pull_request:
     branches: [main]
-    paths:
-      - 'plugins/plotly-express/**'
-      - 'plugins/plotly/**'
-      - 'plugins/matplotlib/**'
-      - 'plugins/json/**'
-      - 'plugins/ui/**'
   push:
     branches: [main]
     tags: