doc: Sync classref with current source

doc/classes/EditorSpatialGizmo.xml

@@ -66,6 +66,8 @@
 			</argument>
 			<argument index="2" name="skeleton" type="RID">
 			</argument>
+			<argument index="3" name="material" type="Material" default="null">
+			</argument>
 			<description>
 			</description>
 		</method>

doc/classes/Engine.xml

@@ -96,7 +96,7 @@
 				"string"   - major + minor + patch + status + build in a single String
 				The "hex" value is encoded as follows, from left to right: one byte for the major, one byte for the minor, one byte for the patch version. For example, "3.1.12" would be [code]0x03010C[/code]. Note that it's still an int internally, and printing it will give you its decimal representation, which is not particularly meaningful. Use hexadecimal literals for easy version comparisons from code:
 				[codeblock]
-				if Engine.get_version_info().hex >= 0x030200:
+				if Engine.get_version_info().hex >= 0x030200:
 				    # do things specific to version 3.2 or later
 				else:
 				    # do things specific to versions before 3.2

editor/spatial_editor_gizmos.cpp

@@ -730,7 +730,7 @@ void EditorSpatialGizmo::set_plugin(EditorSpatialGizmoPlugin *p_plugin) {
 void EditorSpatialGizmo::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("add_lines", "lines", "material", "billboard"), &EditorSpatialGizmo::add_lines, DEFVAL(false));
-	ClassDB::bind_method(D_METHOD("add_mesh", "mesh", "billboard", "skeleton"), &EditorSpatialGizmo::add_mesh, DEFVAL(false), DEFVAL(RID()), DEFVAL(Variant()));
+	ClassDB::bind_method(D_METHOD("add_mesh", "mesh", "billboard", "skeleton", "material"), &EditorSpatialGizmo::add_mesh, DEFVAL(false), DEFVAL(RID()), DEFVAL(Variant()));
 	ClassDB::bind_method(D_METHOD("add_collision_segments", "segments"), &EditorSpatialGizmo::add_collision_segments);
 	ClassDB::bind_method(D_METHOD("add_collision_triangles", "triangles"), &EditorSpatialGizmo::add_collision_triangles);
 	ClassDB::bind_method(D_METHOD("add_unscaled_billboard", "material", "default_scale"), &EditorSpatialGizmo::add_unscaled_billboard, DEFVAL(1));