perf: optimize spawn cleanup removing redundant iteration

src/creatures/monsters/spawns/spawn_monster.cpp

@@ -282,16 +282,17 @@ void SpawnMonster::scheduleSpawn(uint32_t spawnMonsterId, spawnBlock_t &sb, cons
 }
 
 void SpawnMonster::cleanup() {
-	std::vector<uint32_t> removeList;
-	for (const auto &[spawnMonsterId, monster] : spawnedMonsterMap) {
-		if (monster == nullptr || monster->isRemoved()) {
-			removeList.push_back(spawnMonsterId);
+	std::erase_if(spawnedMonsterMap, [this](const auto &entry) {
+		const auto &monster = entry.second;
+		if (!monster || monster->isRemoved()) {
+			auto spawnIt = spawnMonsterMap.find(entry.first);
+			if (spawnIt != spawnMonsterMap.end()) {
+				spawnIt->second.lastSpawn = OTSYS_TIME();
+			}
+			return true;
 		}
-	}
-	for (const auto &spawnMonsterId : removeList) {
-		spawnMonsterMap[spawnMonsterId].lastSpawn = OTSYS_TIME();
-		spawnedMonsterMap.erase(spawnMonsterId);
-	}
+		return false;
+	});
 }
 
 bool SpawnMonster::addMonster(const std::string &name, const Position &pos, Direction dir, uint32_t scheduleInterval, uint32_t weight /*= 1*/) {