Fix the problem in printing feature in c++ API examples : feature_ext…

…ract (#15686)

* fix the problem in printing feature vectors.

Fixed a run-time error caused by mismatch of output dimensions.

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cpp-package/example/feature_extract/feature_extract.cpp

@@ -106,6 +106,7 @@ class FeatureExtractor {
     /*print out the features*/
     auto array = executor->outputs[0].Copy(Context(kCPU, 0));
     NDArray::WaitAll();
+    array = array.Reshape({2, 1024});
     for (int i = 0; i < 1024; ++i) {
       cout << array.At(0, i) << ",";
     }