`--version` not allowed on subcommands, nevertheless listed in the online `--help`

[hacklschorsch]

--help is supported in tahoe subcommands to retrieve more detail, like so::

tahoe run --help

This prints a couple of available subcommands and command-options. One of them is::

--version

But executing tahoe run --version results in tahoe printing an error message::

tahoe: --version not allowed on subcommands

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The online help shouldn't list commands or options that aren't allowed.