Fix the category tree depth calculation issue

Author: dmytro-ch

app/code/Magento/CatalogGraphQl/Model/Resolver/Products/DataProvider/CategoryTree.php

@@ -24,9 +24,9 @@
 class CategoryTree
 {
     /**
-     * In depth we need to calculate only children nodes, so 2 first wrapped nodes should be ignored
+     * In depth we need to calculate only children nodes, so the first wrapped node should be ignored
      */
-    const DEPTH_OFFSET = 2;
+    const DEPTH_OFFSET = 1;
 
     /**
      * @var CollectionFactory

dev/tests/api-functional/testsuite/Magento/GraphQl/Catalog/CategoryTest.php

@@ -63,9 +63,6 @@ public function testCategoriesTree()
           children {
             level
             id
-            children {
-              id
-            }
           }
         }
       }