Fix: Allow bots to duel in PVP prohibited areas (#1906)

Noticed that if you ask a bot to duel in a PVP prohibited area, it will
accept, and do nothing. I thought about making the bot reject the
request, but if you (the real player) want to duel with it, the duel
should happen. This is just a minor fix to allow bots to duel if you ask
them to in such areas.

Tested with bots in party, random bots of the same faction, and random
bots of the opposite faction. All behaved the same before and after fix.
An example place to test is Zim'Torga in Zul'Drak which is by default is
a PVP prohibited area.

- Before fix, you challenge a bot, they accept and turn red, then they
either just stay where they are or wander off.

- After fix, bot attacks you within the PVP prohibited area when the
duel starts.

src/strategy/values/AttackersValue.cpp

@@ -33,18 +33,14 @@ GuidVector AttackersValue::Calculate()
     {
         Unit* unit = botAI->GetUnit(target);
         if (unit && IsValidTarget(unit, bot))
-        {
             targets.insert(unit);
-        }
     }
     if (Group* group = bot->GetGroup())
     {
         ObjectGuid skullGuid = group->GetTargetIcon(7);
         Unit* skullTarget = botAI->GetUnit(skullGuid);
         if (skullTarget && IsValidTarget(skullTarget, bot))
-        {
             targets.insert(skullTarget);
-        }
     }
 
     for (Unit* unit : targets)
@@ -61,9 +57,7 @@ GuidVector AttackersValue::Calculate()
         {
             Unit* unit = botAI->GetUnit(guid);
             if (unit && unit->IsPlayer() && IsValidTarget(unit, bot))
-            {
                 result.push_back(unit->GetGUID());
-            }
         }
     }
 
@@ -110,9 +104,8 @@ void AttackersValue::AddAttackersOf(Player* player, std::unordered_set<Unit*>& t
 
         if (player->IsValidAttackTarget(attacker) &&
             player->GetDistance2d(attacker) < sPlayerbotAIConfig->sightDistance)
-        {
             targets.insert(attacker);
-        }
+
         ref = ref->next();
     }
 }
@@ -180,8 +173,9 @@ bool AttackersValue::IsPossibleTarget(Unit* attacker, Player* bot, float /*range
     if (!bot->CanSeeOrDetect(attacker))
         return false;
 
-    // PvP prohibition checks
+    // PvP prohibition checks (skip for duels)
     if ((attacker->GetGUID().IsPlayer() || attacker->GetGUID().IsPet()) &&
+        (!bot->duel || bot->duel->Opponent != attacker) &&
         (sPlayerbotAIConfig->IsPvpProhibited(attacker->GetZoneId(), attacker->GetAreaId()) ||
         sPlayerbotAIConfig->IsPvpProhibited(bot->GetZoneId(), bot->GetAreaId())))
     {