0x7b is the encoding for SIMD v128 types, so it will become valid when
we turn SIMD on by default. Use kWasmStmt (0x40) instead, it is not a
valid in the function signature position (which requires a value type).

Bug: v8:11511
Change-Id: Ife152e81d831a059a0122f9255897d97b5dc4fc9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2739054
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73232}