cfi/ignores.txt: Add dav1d's ref.c to cfi-icall ignorelist

When dav1d is used from CrabbyAvif (a rust library), cfi-icall
fails when the callbacks are rust functions. Disable cfi-icall
for ref.c so that cfi-icall checks do not fail in CrabbyAvif.

This entry can be removed when we start building Rust CFI with
-Zsanitizer-cfi-normalize-integers and
-fsanitize-cfi-icall-experimental-normalize-integers. This is tracked
in crbug.com/40266913.

Bug: b/323754052
Change-Id: I35342cb18882ace9acbd8aa691e369d3540cd78f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5536152
Reviewed-by: Peter Collingbourne <pcc@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Vignesh Venkat <vigneshv@google.com>
Cr-Commit-Position: refs/heads/main@{#1301447}
NOKEYCHECK=True
GitOrigin-RevId: 4906c54cf24ab1f9f5f7553598683a29f1869c5f