[compiler-rt] [win/asan] GetInstructionSize: Fix `8D A4 24 ...` to return rel_offset=3. (PR #119794)

[Hans Wennborg via llvm-commits]

zmodem wrote:

> `[esp + XX XX XX XX]` is an ESP-relative address, which shouldn't need adjustment, so this change looks dubious to me.

+1 I don't think this should set rel_offset.

https://github.com/llvm/llvm-project/pull/119794