Use BlockPost#atY in end portal softlock fix

patches/server/0803-Prevent-softlocked-end-exit-portal-generation.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Prevent softlocked end exit portal generation
 
 
 diff --git a/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java b/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
-index 93dd5a2d0b550b0373cbf59376a04e9fd6146e92..3cdd3778e8d55bc255a4b6f248b80c04ef0c5ad1 100644
+index 93dd5a2d0b550b0373cbf59376a04e9fd6146e92..53001f490f374c75e0d44ec75387f4bee6ab8952 100644
 --- a/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
 +++ b/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
 @@ -409,6 +409,12 @@ public class EndDragonFight {
@@ -14,7 +14,7 @@ index 93dd5a2d0b550b0373cbf59376a04e9fd6146e92..3cdd3778e8d55bc255a4b6f248b80c04
  
 +        // Paper start - Prevent "softlocked" exit portal generation
 +        if (this.portalLocation.getY() <= this.level.getMinBuildHeight()) {
-+            this.portalLocation.setY(this.level.getMinBuildHeight() + 1);
++            this.portalLocation = this.portalLocation.atY(this.level.getMinBuildHeight() + 1);
 +        }
 +        // Paper end
 +