When handling the 'end' opcode, there was a confusion with the value of
"unreachable". This DCHECK assumes the value of "unreachable" before
closing the scope, but was placed after the value is potentially updated
to reflect the state after the 'end' opcode.

R=clemensb@chromium.org

Bug: chromium:1251845
Change-Id: Iea526e6485fa705f6ff4077f54a53204cc70a926
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3190102Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77116}