Temprorary disable Wasm2C and Wasm2C2Wasm in fuzz_opt

[MaxGraey]

Fix #4723

[kripken]

Reading wasm-binary.h, I think 0x4f (mentioned in #4723) means an isorecursive recursion group, which is a wasm GC type structure. I think we should just disable wasm2c on wasm GC. But looks like that's already the case,

binaryen/scripts/fuzz_opt.py

Line 701 in 4c810e4

return all_disallowed(['exception-handling', 'simd', 'threads', 'bulk-memory', 'nontrapping-float-to-int', 'tail-call', 'sign-ext', 'reference-types', 'multivalue', 'gc'])

So I'm not sure what's going wrong here. It would be good to investigate and see why we run with GC (why that code fails to stop us).

[MaxGraey]

Could that change be a reason? #4633. I guess wabt/wasm2c doesn't have similar changes

[kripken]

That could be a separate reason. But like recursion groups, externref is only used in GC, and we should already be skipping wasm2c with GC, so that needs to be figured out.

[MaxGraey]

Closed in favour of #4738