dont support `:in` parameter for run

remove in parameter

When we changed to `Open3.capture3` we stopped supporting `:in`. It currently silently eats the parameter.

I added the following code to `awesome_spawn_spec`, but it did not work.
If you can think of any obvious issues with this code, then that would be great great.

```
require 'tempfile'
it ":in" do
  tmp = Tempfile.new('foo')
  begin
    tmp.write("line1\nline2")
    tmp.rewind
    # data is not getting read
    result = subject.send(run_method, "cat", :in => tmp)
    expect(result.exit_status).to eq(0)
    expect(result.output).to      eq("line1\nline2")
  ensure
     tmp.close
     tmp.unlink
  end
end
```

//cc @jrafanie This changes the error message, so has a conflict with the other PR.
After you merge one, let me know and I'll fix the other one.