[WASM] Disable simd test case for WASI OS

simd api maybe stable in future https://github.com/WebAssembly/simd

Author: kateinoigakukun

test/stdlib/simd_diagnostics.swift

@@ -1,7 +1,7 @@
 // RUN: %target-typecheck-verify-swift
 
 // FIXME: No simd module on linux rdar://problem/20795411
-// XFAIL: linux, windows
+// XFAIL: linux, windows, wasm
 
 import simd