FeedValidator was fixed upstream; it doesn't use an allowlist of (X)HTML
attributes anymore. After updating FeedValidator to the latest commit, I
don't need to filter out false-positives for these attributes.
The FeedValidator commit that resolved the issue:
0b130bd5d7
- Replace achecker flags with a config file
- Bring back webhint
- Amend check-whole-site so that it will deploy to staging if all checks
pass, and then run webhint on every staging page.
