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: #20610
Reviewed-By: Vse Mozhet Byt <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: ryzokuken

doc/api/http2.md

@@ -846,6 +846,8 @@ the `http2stream.rstCode` property. 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`.