Cleanup, re-implementations

core/src/mindustry/game/Gamemode.java

@@ -11,7 +11,6 @@ public enum Gamemode{
     survival(rules -> {
         rules.waveTimer = true;
         rules.waves = true;
-        rules.unitDrops = true;
     }, map -> map.spawns > 0),
     sandbox(rules -> {
         rules.infiniteResources = true;
@@ -20,7 +19,6 @@ public enum Gamemode{
         rules.respawnTime = 0f;
     }),
     attack(rules -> {
-        rules.unitDrops = true;
         rules.attackMode = true;
     }, map -> map.teams.contains((int)state.rules.waveTeam.id)),
     pvp(rules -> {