Remove the search vignette from navbar and / or transfer doc to ?build_search

[olivroy]

There's little enough in that vignette, I think I'd almost prefer going in the opposite direction — just point to ?build_search from the vignette. (And then maybe remove the vignette from the main navbar since it will only apply to BS3. Or maybe even remove it altogether with a redirect since BS3 is deprecated?)

Originally posted by @hadley in #2562 (comment)

Also, remove mentions to vignette("search") in docs and point to build_search()?