cppgc: Cleanup unittests

The tests using the recursive function were broken on non-clang builds
as GCC is able to agressively the function in question and proof that
parameters are not actually needed.

Bug: chromium:1056170
Change-Id: Iacbff766ca9d300c9ae5d16394e205b1883609eb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2130274
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66952}