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/removed/1.20/0571-copy-TESign-isEditable-from-snapshots.patch

@@ -3,7 +3,9 @@ From: Shane Freeder <theboyetronic@gmail.com>
 Date: Tue, 23 Mar 2021 06:43:30 +0000
 Subject: [PATCH] copy TESign#isEditable from snapshots
 
-
+Dropped in 1.20 as isEditable no longer exists and the full uuid of the editing player
+is stored. New API is needed, but the current #setEditable only mutates the is_waxed state of a sign, which
+is part of the compound tag and hence already copied by applyTo.
 diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java b/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java
 index 97028a14830384f06f4f1de36abfbc6bc1b90a19..a7d75d33367933fdec27538cde5a53cd41f3c252 100644
 --- a/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java