[locale] Document change to the way GeoIPURL is handled.

src/modules/locale/locale.conf

@@ -19,15 +19,18 @@ zone:                       "New_York"
 
 # GeoIP settings. Leave commented out to disable GeoIP.
 #
-# An HTTP request is made to http://*geoipUrl*/json (which just happens
-# to be the GET path needed by freegeoip.net, so calling this a URL
-# is a stretch). The request must return valid JSON data; there should
+# An HTTP request is made to *geoipUrl* -- prior to Calamares 3.1.13,
+# an implicit "/json" was added at the end.. The request must return
+# valid JSON data in the FreeGeoIP format; there should
 # be an attribute *time_zone*, with a string value set to the
-# timezone, in <region>/<zone> form.
+# timezone, in <region>/<zone> format.
+#
+# Note that this example URL works, but the service is shutting
+# down in June 2018.
 #
 # Suitable data looks like
 # ```
 #    {"time_zone":"America/New_York"}
 # ```
 #
-#geoipUrl:                  "freegeoip.net"
+#geoipUrl:                  "freegeoip.net/json"