System fonts are temporarily leaked on Linux after the browser is updated from 12.5a4 or earlier

@pierov 12.0.6 stable returns 134 (all bundled) fonts

alpha returns that plus some non-bundled fonts. IDK if there is an issue open for this, but it I thought we had this sorted out. I think you mentioned using the whitelist as a fallback (but then the test wouldn't pick up font config issues - but that's better than leaking)

Here's my ubunutu VM