[wasm] Remove the use of the "external" bit on OldFunctions section.

test/unittests/wasm/ast-decoder-unittest.cc

Index: test/unittests/wasm/ast-decoder-unittest.cc
diff --git a/test/unittests/wasm/ast-decoder-unittest.cc b/test/unittests/wasm/ast-decoder-unittest.cc
index d986653a35cb60b66a089bf38756068db2931ea1..5972a2825cb85bdceb4ff09b2c24b48d3362915e 100644
--- a/test/unittests/wasm/ast-decoder-unittest.cc
+++ b/test/unittests/wasm/ast-decoder-unittest.cc
@@ -1181,8 +1181,7 @@ class TestModuleEnv : public ModuleEnv {
                              0,        // local_i64_count
                              0,        // local_f32_count
                              0,        // local_f64_count
-                             false,    // exported
-                             false});  // external
+                             false});  // exported
     CHECK(mod.functions.size() <= 127);
     return static_cast<byte>(mod.functions.size() - 1);
   }