Update erltrek_shell.erl

* Fix record type mismatch in #command.name, due to the following
  dialyzer output:

      erltrek_shell.erl:159: Record construction #command{name::string(),expand::boolean(),desc::nonempty_string(),help::nonempty_string(),dispatch::fun(([any()]) -> 'ok')} violates the declared type of field name::atom()

  In get_expand_fun/0, Commands#command.name is assigned by NameL, which is a list.

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