NetworkSession: send FLYING flag on spectator ability layer

fixes #5722

I'm not very clear why this works. PM doesn't use real spectator mode yet (we're still using the faux spectator mode PM has had for years, because I haven't yet assessed how real spectator mode will affect stuff like block interactions), so this ability layer shouldn't have any effect.

thank you @Alemiz112

Author: dktapps

src/network/mcpe/NetworkSession.php

@@ -894,6 +894,12 @@ public function syncAbilities(Player $for) : void{
 			[
 				//TODO: dynamic flying speed! FINALLY!!!!!!!!!!!!!!!!!
 				new AbilitiesLayer(AbilitiesLayer::LAYER_BASE, $boolAbilities, 0.05, 0.1),
+
+				//TODO: HACK! In 1.19.80, the client starts falling in our faux spectator mode when it clips into a
+				//block. I have no idea why this works, since we don't actually use the real spectator mode.
+				new AbilitiesLayer(AbilitiesLayer::LAYER_SPECTATOR, [
+					AbilitiesLayer::ABILITY_FLYING => true,
+				], null, null)
 			]
 		)));
 	}