Drop manual isEditable copy in CraftSign

Signs no longer have a specific isEdiable state, the entire API in this
regard needs updating/deprecation. The boolean field is completely gone,
replaced by a uuid (which will need a new setEditingPlayer(UUID) method
on the Sign interface), and the current upstream implementation of
setEdiable simply flips the is_waxed state.

This patch is hence not needed as it neither allows editing (which will
be redone in a later patch) nor is required to copy the is_waxed boolean
flag as it lives in the signs compound tag and is covered by applyTo.

patches/server/0627-add-per-world-spawn-limits.patch

@@ -1,25 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: chase <chasewhip20@gmail.com>
-Date: Wed, 2 Dec 2020 22:43:39 -0800
-Subject: [PATCH] add per world spawn limits
-
-Taken from #2982. Credit to Chasewhip8
-
-diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-index 02e49e0228667fc88da8347ea6cdf477c13321b7..2d04be33b7450bd4d71c0f80c28efcbde6559142 100644
---- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-@@ -213,6 +213,13 @@ public class CraftWorld extends CraftRegionAccessor implements World {
-         this.biomeProvider = biomeProvider;
- 
-         this.environment = env;
-+        // Paper start - per world spawn limits
-+        for (SpawnCategory spawnCategory : SpawnCategory.values()) {
-+            if (CraftSpawnCategory.isValidForLimits(spawnCategory)) {
-+                setSpawnLimit(spawnCategory, this.world.paperConfig().entities.spawning.spawnLimits.getInt(CraftSpawnCategory.toNMS(spawnCategory)));
-+            }
-+        }
-+        // Paper end
-     }
- 
-     @Override