http: simplify checkIsHttpToken()

Replace code optimized for older versions of V8 with more
straightforward code in checkIsHttpToken().

PR-URL: https://github.com/nodejs/node/pull/17399


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>