[wasm] Remove single function JIT support.

src/wasm/ast-decoder.h

Index: src/wasm/ast-decoder.h
diff --git a/src/wasm/ast-decoder.h b/src/wasm/ast-decoder.h
index 527bb2e4780ba84bc1bafc547e6ed10431c9abf5..c4f6c1679a0bfb89d6d1b9c9c9197305e25aeca2 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -148,16 +148,6 @@ struct CallImportOperand {
   }
 };
 
-struct JITSingleFunctionOperand {
-  uint32_t sig_index;
-  FunctionSig* sig;
-  unsigned length;
-  inline JITSingleFunctionOperand(Decoder* decoder, const byte* pc) {
-    sig_index = decoder->checked_read_u32v(pc, 1, &length, "signature index");
-    sig = nullptr;
-  }
-};
-
 struct BranchTableOperand {
   uint32_t arity;
   uint32_t table_count;