DB/Gilneas: added some terrainswap data to chapter 1 creatures and added two missing sparring entries

sql/updates/world/custom/custom_2019_05_18_01_world.sql

@@ -0,0 +1,6 @@
+DELETE FROM `creature_sparring_template` WHERE `CreatureID` IN (50471, 50474);
+INSERT INTO `creature_sparring_template` (`CreatureID`, `HealthLimitPct`) VALUES
+(50471, 85.0),
+(50474, 85.0);
+
+UPDATE `creature` SET `terrainSwapMap`= 638 WHERE `id` IN (35229, 36057, 35317);