TSG: Add missing NOTE_DEFENSE_CAP

Three units with movement_type=mounted were missing {NOTE_DEFENSE_CAP}

data/campaigns/The_South_Guard/units/Horseman_Commander.cfg

@@ -25,6 +25,7 @@
     description= _ "Leaders of the border guards, mounted commanders command the garrisons that keep peace in the outermost provinces of Wesnoth. As effective leaders and powerful warriors, these men patrol the countryside and eliminate any and all threats to peace in the frontier villages."
     {NOTE_LEADERSHIP}
     {NOTE_CHARGE}
+    {NOTE_DEFENSE_CAP}
     die_sound=horse-die.ogg
     [attack]
         name=lance

data/campaigns/The_South_Guard/units/Junior_Commander.cfg

@@ -24,6 +24,7 @@
     [/abilities]
     description= _ "At scarcely 17 or 18 years of age, squires are not yet full knights, but still have the knowledge and skill to master their mounts whilst in full panoply. Talented squires are sometimes given command of small units in Wesnoth' s army, where they gain experience leading fellow troops and honing their prowess in battle."
     {NOTE_LEADERSHIP}
+    {NOTE_DEFENSE_CAP}
     die_sound=horse-die.ogg
     [attack]
         name=spear

data/campaigns/The_South_Guard/units/Mounted_General.cfg

@@ -26,6 +26,7 @@
     description= _ "Switching seamlessly between lance and mace, mounted generals boast tremendous skill in individual combat and can hold their own against even the most powerful opposition. They are masters of their mounts, able to cover great distances quickly on their patrols, and have keen eyes for detecting and eliminating all manner of perilous dangers. Their greatest strength, however, lies in their ability to inspire great courage in their men, who fight fearlessly and tenaciously under their command."
     {NOTE_LEADERSHIP}
     {NOTE_CHARGE}
+    {NOTE_DEFENSE_CAP}
     die_sound=horse-die.ogg
     [attack]
         name=lance