Update GLTFExporter.js

Remove optional chaining.

examples/jsm/exporters/GLTFExporter.js

@@ -1888,7 +1888,7 @@ class GLTFWriter {
 
 		const attrNamePrefix = attributeName.split( '_', 1 )[ 0 ];
 
-		if ( KHR_mesh_quantization_ExtraAttrTypes[ attrNamePrefix ]?.includes( attrType ) ) {
+		if ( KHR_mesh_quantization_ExtraAttrTypes[ attrNamePrefix ] || KHR_mesh_quantization_ExtraAttrTypes[ attrNamePrefix ].includes( attrType ) ) {
 
 			this.extensionsUsed[ KHR_MESH_QUANTIZATION ] = true;
 			this.extensionsRequired[ KHR_MESH_QUANTIZATION ] = true;