This is not as much of a big story as it is fuel to a previous rumor. According to a screencap courtesy FavBrowser, Facebook has ditched Chrome on its recommended browser landing page and opted to suggest users download the latest version of Opera instead.
You can't check out that page though, as it no longer exists - you'll be redirected to the homepage (if you try to access it via Safari on mobile you get an error page). But you can check out this cached version.
Of course, the significance of this lies in a recent rumor that has Facebook acquiring Opera Software, makers of the Opera browser.
Now, as far as that rumor goes, it makes sense. Facebook hasn't been shy about big acquisitions lately, and this would in no way be as earth shattering as a recent sepia-toned purchase. Then again, it's not like Facebook has a clean plate right now.
Naturally, an Opera sighting on an official Facebook page will perpetuate the rumors. But it's not like Facebook has gone nuclear on Chrome. A quick look at Facebook's help page on supported browsers looks like this: