TSG: Removed obsolete geography-related comment

The comment dates back to when the campaign had no proper bigmap, and with the current bigmap it's clear where everything is situated.

data/campaigns/The_South_Guard/utils/sg_story.cfg

@@ -1,18 +1,5 @@
 #textdomain wesnoth-tsg
 
-# Geographical assumptions:
-#
-# This campaign was apparently designed before the geography of Wesnoth
-# was fixed to the main map -- there was a reference in it to unknown forest
-# south of the "Great River", which doesn't fit at all. To rescue this, the
-# original tSG Great River has to be either the unnamed river running through
-# the Aethenwood or off the map entirely. I've opted for the latter, thus the
-# reference to Kerlath being "in the furthermost south", and renamed the river
-# as the "Black River". Since the original campaign placed the "elvish woods"
-# west of Westin, I'm supposing they're in fact a southern (off-map) lobe
-# of the Aethenwood.
-#
-
 #define SG_BORN_TO_THE_BANNER
     [story]
         [part]