The hash of signatures currently has redundancy: We hash both the
parameter count and the return count, plus all contained values.
The total count of contained values is already implicitly captured by
{hash_combine}ing the individual values, thus it's enough to only
include one of parameter count and return count.

R=manoskouk@chromium.org

Bug: v8:12593
Change-Id: I6d3e8b15f4251964e3a74ae5411d06a7d41183a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3460415Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79095}