Make buttons closer in Scene tree

(cherry picked from commit a911b1f126b60d8d119e15eade30fd40692f8ddf)

editor/scene_tree_editor.cpp

@@ -1110,6 +1110,7 @@ SceneTreeEditor::SceneTreeEditor(bool p_label, bool p_can_rename, bool p_can_ope
 	tree->set_anchor(MARGIN_BOTTOM, ANCHOR_END);
 	tree->set_begin(Point2(0, p_label ? 18 : 0));
 	tree->set_end(Point2(0, 0));
+	tree->add_constant_override("button_margin", 0);
 
 	add_child(tree);