[wasm] Remove wrong DCHECK

Empty function bodies can actually reach the compiler. We could prevent
this by making this a decoder error instead, but that would be a
redundant check, so we should just remove the DCHECK instead.

R=ahaas@chromium.org

Bug: chromium:1219898
Change-Id: Ie1bed30cee44be9ac42b5f5f980a122c8dc8b2ec
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2966385


Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75191}