www/py-autobahn: Remove ACCELERATE OPTION

autobahn now ships with it's own NVX accelerator and upstream has
removed wsaccel support.

Changelog: https://github.com/crossbario/autobahn-python/releases/tag/v${NEW_VERSION}
(cherry picked from commit c969f7008f681912501f7838f2b9c49f3b5b0071)