Make Firefox notes around documeny.body consistent with other notes (#10683)
Make Firefox notes around documeny.body consistent with other notes (#10683)

Fixes https://github.com/mdn/browser-compat-data/issues/6839.

https://github.com/mdn/browser-compat-data/issues/10682 tracks using
this structure consistently where there's currently just a simple
statement.
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data