Update OBJLoader.html (#10009)

Spelling correction.

docs/api/loaders/OBJLoader.html

@@ -47,7 +47,7 @@
 		<div>
 		Returns an [page:Object3D]. It contains the parsed meshes as [page:Mesh] and lines as [page:LineSegments].<br />
 		All geometry is created as [page:BufferGeometry]. Default materials are created as [page:MeshPhongMaterial].<br />
-		If an <em>obj</em> object or group uses multiple materials while declaring faces geometry groups and an [page:MultiMaterial] is used.
+		If an <em>obj</em> object or group uses multiple materials while declaring faces geometry groups and a [page:MultiMaterial] is used.
 		</div>
 
 		<h2>Example</h2>