[WebNN] Fix bug in Float16Array availability check (microsoft#25354)

The `from` is not a property of `Float16Array` but an inherited
function, we can use `Float16Array['from']` to check if it is available.

Author: Honry

onnxruntime/core/providers/webnn/builders/impl/rotaryEmbedding_op_builder.cc

@@ -285,7 +285,7 @@ Status RotaryEmbeddingOpBuilder::AddToModelBuilderImpl(ModelBuilder& model_build
     sign_buffer.set(1, 1.0f);
   } else if (input_data_type == ONNX_NAMESPACE::TensorProto_DataType_FLOAT16) {
     if (model_builder.IsFloat16ArrayAvailable()) {
-      // Float16Array is avaliable - use Float16Array.
+      // Float16Array is available - use Float16Array.
       sign_buffer = emscripten::val::global("Float16Array").new_(2);
       sign_buffer.set(0, -1.0f);
       sign_buffer.set(1, 1.0f);

onnxruntime/core/providers/webnn/builders/model_builder.h

@@ -78,7 +78,7 @@ class ModelBuilder {
   const GraphViewer& graph_viewer_;
   const logging::Logger& logger_;
   const bool is_float16array_available_ = !emscripten::val::global("Float16Array").isUndefined() &&
-                                          emscripten::val::global("Float16Array").hasOwnProperty("from");
+                                          !emscripten::val::global("Float16Array")["from"].isUndefined();
 
   emscripten::val wnn_context_ = emscripten::val::undefined();
   emscripten::val wnn_builder_ = emscripten::val::undefined();