Update screenshot for guide

[tabesin]

https://github.com/fossasia/meilix/blob/master/docs/run_meilix_with_qemu.md
shows a screenshot of Lubuntu starting.

[SidharajYadav]

hi, I am new to open source. I was looking at some good first issues. Can I work on this?

[abishekvashok]

@SidharajYadav sure