SotA clarifications and prose edits. (wesnoth#6168)

* SotA S6 Provide better tomato surprise hint. (fix wesnoth#6120)

* SotA S2 Add objective note about guardhouse. (fix wesnoth#6121)

* SotA S4 Add objective note. (fix wesnoth#6123)

data/campaigns/Secrets_of_the_Ancients/scenarios/02_Dark_Business.cfg

@@ -573,7 +573,7 @@ of Healing"
             # This puts images of the two units next to each other,
             # scaled to the same size:
             image=story/black-background.png~BLIT(portraits/undead/archer.png~SCALE(180,180),6,25 )~BLIT(portraits/undead/skeleton.png~SCALE(220,220),187,0)~CROP(0,0,376,205)~SCALE(171,93)
-            message= _ "You can now recruit skeletons and skeleton archers!"
+            message= _ "You can now recruit skeletons and skeleton archers! You will lose this ability if the guardhouse is retaken by the guards!"
         [/message]
         [set_variable]
             name=can_recruit_skeletons

data/campaigns/Secrets_of_the_Ancients/scenarios/04_Becalmed.cfg

@@ -259,6 +259,9 @@ The journey started well enough, but on the dawn following our departure, the wi
             [note]
                 description= _ "You can recruit from anywhere on the two highest decks."
             [/note]
+            [note]
+                description= _ "Player and Enemy units can move between the surface and the interior of the ship via stairs."
+            [/note]
             [note]
                 description= _ "Barrels act as villages."
             [/note]

data/campaigns/Secrets_of_the_Ancients/scenarios/06_Following_the_Shadow.cfg

@@ -250,7 +250,7 @@ I was so sure I had the answer! I was wrong. I wanted to believe that I was imag
         [/delay]
         [message]
             speaker=Ardonna
-            message= _ "If there is one bat, there are certainly more. We should be careful."
+            message= _ "If there is one bat, there are certainly more. We should be careful. It would be foolish to explore this cave alone."
         [/message]
     [/event]