Make `Polygon2D::bones` property internal

doc/classes/Polygon2D.xml

@@ -71,9 +71,6 @@
 		<member name="antialiased" type="bool" setter="set_antialiased" getter="get_antialiased" default="false">
 			If [code]true[/code], polygon edges will be anti-aliased.
 		</member>
-		<member name="bones" type="Array" setter="_set_bones" getter="_get_bones" default="[]">
-			Internal list of [Bone2D] nodes used by the assigned [member skeleton]. Edited using the Polygon2D editor ("UV" button on the top toolbar).
-		</member>
 		<member name="color" type="Color" setter="set_color" getter="get_color" default="Color(1, 1, 1, 1)" keywords="colour">
 			The polygon's fill color. If [member texture] is set, it will be multiplied by this color. It will also be the default color for vertices not set in [member vertex_colors].
 		</member>

scene/2d/polygon_2d.cpp

@@ -682,7 +682,7 @@ void Polygon2D::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::PACKED_VECTOR2_ARRAY, "uv"), "set_uv", "get_uv");
 	ADD_PROPERTY(PropertyInfo(Variant::PACKED_COLOR_ARRAY, "vertex_colors"), "set_vertex_colors", "get_vertex_colors");
 	ADD_PROPERTY(PropertyInfo(Variant::ARRAY, "polygons"), "set_polygons", "get_polygons");
-	ADD_PROPERTY(PropertyInfo(Variant::ARRAY, "bones", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR), "_set_bones", "_get_bones");
+	ADD_PROPERTY(PropertyInfo(Variant::ARRAY, "bones", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR | PROPERTY_USAGE_INTERNAL), "_set_bones", "_get_bones");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "internal_vertex_count", PROPERTY_HINT_RANGE, "0,1000"), "set_internal_vertex_count", "get_internal_vertex_count");
 }