K parameter has no effect in KNN classifier

Bug reported by users on the forum

When using the KNN classifier, for example in TrainVectorClassifier or TrainImageClassifier, the input number of neighbor has no impact on the trained classifier.

Step to reproduce: (OTB 7.2.0)

otbcli_TrainVectorClassifier -io.vd trainExtract.shp   -io.out knn.txt  -cfield classlabel -feat value_0 value_1       -classifier knn -valid.vd validExtract.shp -classifier.knn.k  10
[...]
2021-04-16 11:43:46 (INFO) TrainVectorClassifier: Confusion matrix (rows = reference labels, columns = produced labels):
    [0] [1] [2] [3] 
[0]  25   0   1   0 
[1]   0 296   0   0 
[2]   9   0  76   7 
[3]   0  21   0 593 
[...]

otbcli_TrainVectorClassifier -io.vd trainExtract.shp   -io.out knn.txt  -cfield classlabel -feat value_0 value_1       -classifier knn -valid.vd validExtract.shp -classifier.knn.k  1
[...]
2021-04-16 11:43:46 (INFO) TrainVectorClassifier: Confusion matrix (rows = reference labels, columns = produced labels):
    [0] [1] [2] [3] 
[0]  25   0   1   0 
[1]   0 296   0   0 
[2]   9   0  76   7 
[3]   0  21   0 593 
[...]