Only consider immediate descendant infoboxes while moving first paragraph

If the first paragraph in the lead section comes after infoboxes, then
it is moved above those infoboxes that are immediate children of
the lead section. If an infobox is wrapped in a container then
it's ignored and no relocation is done.

This only affects beta users.

Bug: T149389
Change-Id: I851918544a3df69fb5e4f9463b41fb03d7ef520c