Image recs: insert into infobox only for English.

[dbrant]

For the logic that attempts to insert the image into an infobox, we are supposed to be restricting it only to English, because we only have hardcoded infobox names and parameters in English.
But it looks like we're incorrectly falling back to English, and detecting infoboxes implicitly, which can lead to undesirable cases: for example French Wikipedia also uses a template called Infobox, but the parameter names are different (e.g. légende instead of caption), so let's add add an explicit check.

https://phabricator.wikimedia.org/T365252