BufferGeometry: Reverted computeFaceNormals removal (because unit tests...)

src/core/BufferGeometry.js

@@ -733,6 +733,12 @@ BufferGeometry.prototype = Object.assign( Object.create( EventDispatcher.prototy
 
 	},
 
+	computeFaceNormals: function () {
+
+		// backwards compatibility
+
+	},
+
 	computeVertexNormals: function () {
 
 		const index = this.index;