Remove "TorButton > Preferences > Proxy Settings" Tab

As far as I understand, this tab is redundant or mostly redundant. One of the UX test users was confused by it. For example, I'm confident nobody is using Gopher or FTP settings. It would be nice to remove the entire tab, if possible. If there are any features or options still needed, we could move them to the "Torbutton > Open Network Settings" window.

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