Fix Lexer deprecation

[jmsche]

Hi,

This (very) small PR to fix a lexer deprecation:

Accessing Doctrine\Common\Lexer\Token properties via ArrayAccess is deprecated, use the value, type or position property instead (Token.php:104 called by Parser.php:585, doctrine/lexer#79, package doctrine/lexer)

I think the fix is okay for 2.15.x branch as it requires doctrine/lexer:^2.

[greg0ire]

Thanks for this, but I'll close in favor of #10737 , which covers more cases.