benchmark: shorten config name in http benchmark

Shorten the config name in check_invalid_header_char so it would
not result in long lines that make the benchmark result hard to read.

PR-URL: https://github.com/nodejs/node/pull/18452


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>