Update participants.mdx

[shurinov]

Fix real flags in namadac utils init-genesis-established-account ...
--alias should be changed to --aliases
according to binary help

namadac utils init-genesis-established-account --help
Initialize an established account available at genesis.

Usage: namadac utils init-genesis-established-account [OPTIONS] --path <path>

Options:
      --aliases <aliases>...   Comma separated list of aliases of the keys to use from the wallet.
      --threshold <threshold>  The minimum number of signatures to be provided for authorization. Must be less than or equal to the maximum number of key aliases provided.
      --vp <vp>                The validity predicate of the account. Defaults to `vp_user`.
      --path <path>            The path of the .toml file to write the established account transaction to. Overwrites the file if it exists.
  -h, --help                   Print help

[bengtlofgren]

Thank you! This pr was closed in favour of #219