Fix url to first-colo website in footer.

As advised by hpekdemir from the company.
````
<infirit> Which one?
<hpekdemir> the one on the bottom. "Hosted by First Colo"
<infirit> It points to http://www.first-colo.net/EN/ right now
<hpekdemir> this is First Colo. Hosting of mate-desktop.org. We changed our website, so the provided link on mate-desktop.org isn't up to date anymore. Please change to first-colo.com
<infirit> Ah ok I see
<infirit> hpekdemir, I'll look into it and correct it
````