welcome: disable geoip by default (and document how)

FIXES #1148

src/modules/welcome/welcome.conf

@@ -55,8 +55,12 @@ requirements:
 # connectivity, though. Configuration is like in the locale module,
 # but remember to use a URL that returns full data **and** to
 # use a selector that will pick the country, not the timezone.
+#
+# To disable, either comment-out the entire section, or set
+# the *style* key to an unsupported format (e.g. `none`, as is
+# done here).
 
 geoip:
-    style:  "xml"
+    style:  "none"
     url:    "https://geoip.kde.org/v1/ubiquity"  # extended XML format
     selector: "CountryCode"  # blank uses default, which is wrong