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/0797-Fix-saving-in-unloadWorld.patch

@@ -1,20 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Philip Kelley <philip@thoriumcube.org>
-Date: Wed, 16 Mar 2022 12:05:59 +0000
-Subject: [PATCH] Fix saving in unloadWorld
-
-Change savingDisabled to false to ensure ServerLevel's saving logic gets called when unloadWorld is called with save = true
-
-diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-index 3ed58a87e08ab22a39d4c3b3fbe0b2ea9e3747f8..c020acc1bcfe3471728c143862625463d7c82dd8 100644
---- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
-@@ -1313,7 +1313,7 @@ public final class CraftServer implements Server {
- 
-         try {
-             if (save) {
--                handle.save(null, true, true);
-+                handle.save(null, true, false); // Paper - don't disable saving
-             }
- 
-             handle.getChunkSource().close(save);