[Instrumented libraries] Update libffi6 to libffi7 for Focal

R=thestig

Bug: 1260217
Change-Id: I5fad96e82ec0e7b29b966c549080cdcc5c2a9e06
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3262607
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#938650}
NOKEYCHECK=True
GitOrigin-RevId: 4b7826e79e9cad3496cab5644456494282039da0