Explicitly delete unused result to avoid memory leak

Author: lina128

tfjs-backend-wasm/src/kernels/NonMaxSuppressionV3.ts

@@ -64,9 +64,12 @@ function kernelFunc(args: {
   const resOffset =
       wasmFunc(boxesId, scoresId, maxOutputSize, iouThreshold, scoreThreshold);
 
-  const {pSelectedIndices, selectedSize} =
+  const {pSelectedIndices, selectedSize, pSelectedScores} =
       parseResultStruct(backend, resOffset);
 
+  // Since we are not using scores for V3, we have to delete it from the heap.
+  backend.wasm._free(pSelectedScores);
+
   const selectedIndicesTensor =
       backend.makeOutput([selectedSize], 'int32', pSelectedIndices);