doc: http2.createServer options as optional

The method might be designed to explicitly take `options`. However,
the implementation and many examples already allow the first parameter
of a function type.

PR-URL: https://github.com/nodejs/node/pull/42832
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

doc/api/http2.md

@@ -2343,7 +2343,7 @@ Throws `ERR_HTTP2_INVALID_SETTING_VALUE` for invalid `settings` values.
 
 Throws `ERR_INVALID_ARG_TYPE` for invalid `settings` argument.
 
-### `http2.createServer(options[, onRequestHandler])`
+### `http2.createServer([options][, onRequestHandler])`
 
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