fix(plugins): Sync FAQ question attribute with Polylang

[rsanchez-beapi]

Summary

• Register blockparty/faq-question → question on pll_blocks_rules_for_attributes so Polylang/Autopoly translates the attribute along with the saved HTML.
• Fixes block validation failures when editing EN (or other translated) pages that contain the FAQ block.

Context

faq-question stores the question both as a JSON attribute and in the HTML. Without the Polylang rules, Autopoly only updated the HTML, leaving the attribute in the source language and breaking Gutenberg validation.

Test plan

• Edit an EN page with a FAQ block: no validation error on faq-question.
• Re-translate (or create a new translation) FR → EN: question attribute and <span> HTML are both in EN.
• Confirm FR source pages are unchanged.
• Note: already broken EN pages may need a re-sync / re-translation after this fix.