Fix difference in translation strings regarding the new Between Two Seas map (#416)

##Description:
I renamed all instances of "TwoSeas" to "BetweenTwoSeas". That way it
lowers the confusion but more importrantly - it removes the difference
between the translation strings for the map.

Please put your Discord username so you can be contacted if a bug or
regression is found:

<Nikola123>

src/client/components/Maps.ts

@@ -21,7 +21,7 @@ export const MapDescription: Record<keyof typeof GameMapType, string> = {
   Australia: "Australia",
   Iceland: "Iceland",
   Japan: "Japan",
-  TwoSeas: "Between Two Seas",
+  BetweenTwoSeas: "Between Two Seas",
   KnownWorld: "Known World",
 };