Even in unreachable code, the targets of br_table have to have matching
types.

R=thibaudm@chromium.org

Bug: v8:10556
Change-Id: I2e85df3cb92f7910a6bcb5ac03927c424194660d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2218062
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68148}