Remove refresh button

[Gireen]

fix Unvanquished/Unvanquished#1156

[illwieckz]

The refresh button in LAN tab also have to be removed.

Also, I now think that once the "Refresh" button is removed, the remaining all-in-one button (the one for Internet servers and the one for LAN servers) can just be named "Refresh", as there is no need in the button to say it's a server list and the "Refresh" word is now available.

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Note: this is just information about what may be future changes after that.

My dream would be to have only one list, merging LAN and Internet, like this (Quetoo):

But that's for later.