Document that one shall restart Unsafe Browser after reconnecting to a different network

reported to WhisperBack:

Exact steps to reproduce the error
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1. Connect to a network with a given resolver.
2. Start the Unsafe Browser.
3. Connect to a different network with another resolver.
4. Load a page in the Unsafe Browser.

Actual result and description of the error
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The Unsafe Browser will not be able to load any pages because /etc/resolv.conf
is stuck with the address of the resolver of the first network. Is not fixed when restarting the Unsafe browser neither.

I think that this can be a very annoying usability issue. Let’s say that
you are in an airport and want to try out several captive portals. You should restart Tails every time?

Feature Branch: feature/8243-meek

Original created by @emmapeel on 7903 (Redmine)