Liberty S8: Fix ambiguous pronoun

(cherry-picked from commit 4c61240)

data/campaigns/Liberty/scenarios/08_Glory.cfg

@@ -32,7 +32,7 @@
         [/part]
         [part]
             background=story/Halstead.jpg
-            story= _ "This sentinel of the western plains stood watch as Wesnoth prospered for many centuries under the protection it provided. No war has overcome it, and its walls have never been overrun. The blood of invaders stains its parapets and the bones of the defeated crumble at the base of Halstead’s frozen waves of stone."
+            story= _ "This sentinel of the western plains stood watch as Wesnoth prospered for many centuries under its protection. No war has overcome it, and its walls have never been overrun. The blood of invaders stains its parapets and the bones of the defeated crumble at the base of Halstead’s frozen waves of stone."
         [/part]
     [/story]