qubes-anaconda-addon: adjust option for routing updates through tor

Previously the option was described "Route applications traffic and
updates through Tor anonymity network". This isn't fully accurate
description, and also we decided it's better to provide an option for
routing just updates, not everything.
Also, remove 'experimental' tag.

Fixes QubesOS/qubes-issues#2604

qubes-anaconda-addon/org_qubes_os_initial_setup/gui/spokes/qubes_os.py

@@ -255,10 +255,10 @@ class QubesOsSpoke(FirstbootOnlySpokeMixIn, NormalSpoke):
         else:
             self.choice_whonix = DisabledChoice(_("Whonix not installed"))
 
-        self.choice_whonix_default = QubesChoice(
-            _('Route applications traffic and updates through Tor anonymity '
-              'network [experimental]'),
-            (),
+        self.choice_whonix_updates = QubesChoice(
+            _('Enable system and template updates over the Tor anonymity '
+              'network using Whonix'),
+            ('qvm.updates-via-whonix',),
             depend=self.choice_whonix,
             indent=True)
 
@@ -545,12 +545,13 @@ class QubesOsSpoke(FirstbootOnlySpokeMixIn, NormalSpoke):
         self.set_stage('Setting up networking')
 
         default_netvm = 'sys-firewall'
-        if self.choice_whonix_default.get_selected():
-            default_netvm = 'sys-whonix'
+        updatevm = default_netvm
+        if self.choice_whonix_updates.get_selected():
+            updatevm = 'sys-whonix'
 
         self.run_command(['/usr/bin/qvm-prefs', 'sys-firewall', 'netvm', 'sys-net'])
         self.run_command(['/usr/bin/qubes-prefs', 'default-netvm', default_netvm])
-        self.run_command(['/usr/bin/qubes-prefs', 'updatevm', default_netvm])
+        self.run_command(['/usr/bin/qubes-prefs', 'updatevm', updatevm])
         self.run_command(['/usr/bin/qubes-prefs', 'clockvm', 'sys-net'])
         self.run_command(['/usr/bin/qvm-start', default_netvm])