fixing linting issues

src/lights/LightShadow.d.ts

@@ -21,7 +21,7 @@ export class LightShadow {
 	clone( recursive?: boolean ): this;
 	toJSON(): any;
 	getFrustum(): number;
-	updateMatrices( light: Light ): void;
+	updateMatrices( light: Light, viewportIndex?: number ): void;
 	getViewport( viewportIndex: number ): Vector4;
 	getFrameExtents(): Vector2;
 

src/lights/PointLightShadow.d.ts

@@ -5,6 +5,4 @@ export class PointLightShadow extends LightShadow {
 
 	camera: PerspectiveCamera;
 
-	updateMatrices( light: Light, viewportIndex: number ): void;
-
 }

src/lights/PointLightShadow.js

@@ -58,7 +58,7 @@ PointLightShadow.prototype = Object.assign( Object.create( LightShadow.prototype
 
 	isPointLightShadow: true,
 
-	updateMatrices: function ( light, viewportIndex ) {
+	updateMatrices: function ( light, viewportIndex = 0 ) {
 
 		var camera = this.camera,
 			shadowMatrix = this.matrix,