units: skeleton rider tree deep water patch (#8142)

these two units can now move in deep water and use submerge

data/core/units/undead/Skele_Bone_Knight.cfg

@@ -7,6 +7,13 @@
     image="units/undead-skeletal/boneknight.png"
     hitpoints=50
     movement_type=mounted
+    # adjust to actually use submerge
+    [movement_costs]
+        deep_water=5
+    [/movement_costs]
+    [defense]
+        deep_water=90
+    [/defense]
     {DEFENSE_ANIM "units/undead-skeletal/boneknight-defend1.png" "units/undead-skeletal/boneknight-defend2.png" {SOUND_LIST:SKELETON_BIG_HIT} }
     [movement_anim]
         start_time=0

data/core/units/undead/Skeleton_Rider.cfg

@@ -26,6 +26,13 @@
     [/standing_anim]
     hitpoints=36
     movement_type=mounted
+    # adjust to actually use submerge
+    [movement_costs]
+        deep_water=5
+    [/movement_costs]
+    [defense]
+        deep_water=90
+    [/defense]
     movement=7
     # a cross between the mounted and undeadfoot resistances
     [resistance]