According to the latest wasm-gc spec, the type immediate for the
argument's heap type is no longer required. This CL also adds a missing
check that the rtt immediate is a subtype of the argument's type.

Bug: v8:7742
Change-Id: I627002d1c4bdb4ca3f2181d2f4b659ce3e95cb2d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2642246
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72287}