Update needed to Electrum docs

In the page wiki/src/doc/anonymous_internet/electrum.mdwn (https://tails.boum.org/doc/anonymous_internet/electrum/ ) there is a tip that should be updated:

 
<p><span class="application">Electrum</span> uses <em>mBTC</em> as the
default base unit. 1 mBTC = 0.001 BTC. To change this setting choose
<span class="menuchoice">
  <span class="guimenu">Tools</span>&nbsp;▸
  <span class="guimenuitem">Preference</span></span> and open the
<span class="guilabel">Appearance</span> tab.</p>
 
</div>

But the window has changed, and the option Appearance is not available now, see screenshot:

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