TS: Fix import in InstancedMesh.d.ts

src/objects/InstancedMesh.d.ts

 import { Geometry } from './../core/Geometry';
 import { BufferGeometry } from '../core/BufferGeometry';
 import { Material } from './../materials/Material';
-import { BufferAttribute } from './../core/BufferAttribute.js';
+import { BufferAttribute } from './../core/BufferAttribute';
 import { Mesh } from './Mesh';
 import { Matrix4 } from './../math/Matrix4';