Update 404 detection

[fregante]

• 404 issue: https://github.com/refined-github/refined-github/issues/888888
• 404 file: https://github.com/refined-github/refined-github/blob/main/source/features/a-horse-with-no-name.tsx
• 410 file: https://github.com/refined-github/refined-github/blob/main/extension/content.js
• 404 ref: https://github.com/refined-github/refined-github/blob/eggs-for-branch/package.json