doc: add parameters for Http2Session:error event

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

Refs: nodejs/help#877 (comment)

Backport-PR-URL: #22850
PR-URL: #20206
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Vse Mozhet Byt <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>

Author: ryzokuken

doc/api/http2.md

@@ -149,6 +149,8 @@ connected to the remote peer and communication may begin.
 added: v8.4.0
 -->
 
+* `error` {Error}
+
 The `'error'` event is emitted when an error occurs during the processing of
 an `Http2Session`.