Fix for PHP version 7.1

[milosh012]

Fixing error that we have on old server with PHP ver 7.1.

Error was:

Type error: Return value of AppleSignIn\ASDecoder::decodeIdentityToken() must be an instance of AppleSignIn\object, instance of stdClass returned

Quick fix was just to not expect return type for method decodeIdentityToken

[eddyson1006]

Need this changes to use in PHP 7.1.19