static/frontend/unit/versions/versions.tmpl: reduce vuln chip height
static/frontend/unit/versions/versions.tmpl: reduce vuln chip height

Wrapping the vuln chip in a plain div insulates it from the effects of
the enclosing flex box.

Change-Id: I7a2ca0a43b7170fb2d5e5c8a77c02ec4f34f9857
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/348929
Trust: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Run-TryBot: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Reviewed-by: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite