doc,http2: add parameters for Http2Session:connect event

Add parameters for the callback for the Http2Session:connect event
inline with the pattern in the rest of the documentation.

Refs: https://github.com/nodejs/help/issues/877#issuecomment-381253464

Backport-PR-URL: https://github.com/nodejs/node/pull/22850
PR-URL: https://github.com/nodejs/node/pull/20193


Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>