SotA S21: fix terrain filter

The map has been adjusted before, but not the filter

[ci skip]

(cherry-picked from commit fec49a53a6)

data/campaigns/Secrets_of_the_Ancients/scenarios/21_Against_the_World.cfg

@@ -136,7 +136,7 @@ We finally made it out of the mountains. We crossed the Ford of Abez late this m
             # down the river.
             turns=1-3
             [avoid]
-                terrain=!,Chw,Khw,W*,*^V*
+                terrain=!,C*^*,K*^*,W*^*,*^V*
             [/avoid]
         [/ai]
         {FLAG_VARIANT long}