doc: add parameters for Http2Stream:error event

Add parameters for the callback for the Http2Stream:error event
inline with the pattern in the rest of the documentation.

Refs: nodejs/help#877 (comment)

PR-URL: nodejs#20610
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/http2.md

@@ -850,6 +850,8 @@ code specified when closing the stream. If the code is any value other than
 added: v8.4.0
 -->
 
+* `error` {Error}
+
 The `'error'` event is emitted when an error occurs during the processing of
 an `Http2Stream`.