Fix blog-logo CSS selector in responsiveness.scss

[SirSoySauce]

Firstly, thank you very much for your work on this theme.

I have noticed that the blog logo is not scaled on smaller screens. It seems that the CSS-selector #block-logo img does not work, because the Element with the ID block-logo already is an img-Element and therefore is not referenced. This fix removes the img from the CSS-selector.

Before

After