fix MPP-4189: change debug report filter to allow-list

[groovecoder]

This PR fixes #MPP-4189.

How to test:

1. pytest includes tests for this
2. Make sure DEBUG=True in your local environment
3. Visit http://127.0.0.1:8000/accounts/
   • It should show a 404 page with DEBUG output
4. Expand the DjDT sidebar on the right
5. Click "Settings" to open the settings panel
   • Nearly every setting value should now be '********************'

• l10n changes have been submitted to the l10n repository, if any.
• I've added a unit test to test for potential regressions of this bug.
• I've added or updated relevant docs in the docs/ directory.
• All UI revisions follow the coding standards, and use Protocol / Nebula colors where applicable (see /frontend/src/styles/colors.scss).
• Commits in this PR are minimal and have descriptive commit messages.