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/0777-Add-missing-Validate-calls-to-CraftServer-getSpawnLi.patch

@@ -1,20 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
-Date: Sat, 12 Feb 2022 12:40:50 -0700
-Subject: [PATCH] Add missing Validate calls to CraftServer#getSpawnLimit
-
-Copies appropriate checks from CraftWorld#getSpawnLimit
-
-diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-index 93eff6f651a0f55098f0f7d46b33066d8f88d6a6..31219bb9958673d4f30daea338b0d2d798538758 100644
---- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-@@ -2190,6 +2190,8 @@ public final class CraftServer implements Server {
-     @Override
-     public int getSpawnLimit(SpawnCategory spawnCategory) {
-         // Paper start
-+        Validate.notNull(spawnCategory, "SpawnCategory cannot be null");
-+        Validate.isTrue(CraftSpawnCategory.isValidForLimits(spawnCategory), "SpawnCategory." + spawnCategory + " does not have a spawn limit.");
-         return this.getSpawnLimitUnsafe(spawnCategory);
-     }
-     public int getSpawnLimitUnsafe(final SpawnCategory spawnCategory) {