fix multiline comments

cpp/daal/src/algorithms/dtrees/gbt/regression/test/gbt_regression_model_builder_unit.cpp

@@ -21,10 +21,12 @@ namespace daal::algorithms::gbt::internal
 {
 GbtDecisionTree prepareThreeNodeTree()
 {
- // create a tree with 3 nodes, 1 root (split), 2 leaves
- // ROOT (level 1)
- // / \
- // L L (level 2)
+ /**
+ * create a tree with 3 nodes, 1 root (split), 2 leaves
+ * ROOT (level 1)
+ * / \
+ * L L (level 2)
+ */
  GbtDecisionTree tree = GbtDecisionTree(3, 2);
 
  ModelFPType * splitPoints = tree.getSplitPoints();
@@ -52,13 +54,14 @@ GbtDecisionTree prepareThreeNodeTree()
 
 GbtDecisionTree prepareFiveNodeTree()
 {
- // create a tree with 5 nodes
- // ROOT (1) (level 1)
- // / \
- // L (2) S (3) (level 2)
- // / \
- // L (6) L (7) (level 3)
- // (note: on level 3, nodes 4 and 5 do not exist and will be created as "dummy leaf")
+ /** create a tree with 5 nodes
+ * ROOT (1) (level 1)
+ * / \
+ * L (2) S (3) (level 2)
+ * / \
+ * L (6) L (7) (level 3)
+ * (note: on level 3, nodes 4 and 5 do not exist and will be created as "dummy leaf")
+ */
  GbtDecisionTree tree = GbtDecisionTree(5, 3);
 
  ModelFPType * splitPoints = tree.getSplitPoints();