revert Matrix3 and 4, because of wrong extending in d.ts

src/math/Matrix3.d.ts

@@ -10,7 +10,6 @@ export interface Matrix {
 	 * Array with matrix values.
 	 */
 	elements: number[];
-	isMatrix3: boolean;
 
 	/**
 	 * identity():T;

src/math/Matrix4.d.ts

@@ -30,8 +30,6 @@ export class Matrix4 implements Matrix {
 	 */
 	elements: number[];
 
-	isMatrix4: boolean;
-
 	/**
 	 * Sets all fields of this matrix.
 	 */