remove withCredentials in FileLoader since they're in Loader now

src/loaders/FileLoader.d.ts

@@ -7,7 +7,6 @@ export class FileLoader extends Loader {
 
 	mimeType: undefined | MimeType;
 	responseType: undefined |string;
-	withCredentials: undefined |string;
 
 	load(
 		url: string,
@@ -17,6 +16,5 @@ export class FileLoader extends Loader {
 	): any;
 	setMimeType( mimeType: MimeType ): FileLoader;
 	setResponseType( responseType: string ): FileLoader;
-	setWithCredentials( value: boolean ): FileLoader;
 
 }

src/loaders/FileLoader.js

@@ -286,13 +286,6 @@ FileLoader.prototype = Object.assign( Object.create( Loader.prototype ), {
 
 	},
 
-	setWithCredentials: function ( value ) {
-
-		this.withCredentials = value;
-		return this;
-
-	},
-
 	setMimeType: function ( value ) {
 
 		this.mimeType = value;