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/0574-Expose-protocol-version.patch

@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <nassim@njahnke.dev>
+Date: Fri, 26 Mar 2021 11:23:17 +0100
+Subject: [PATCH] Expose protocol version
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+index 44850ec4a8245bc534efb85008486dd6f599b2e4..fb24efa54510fc77a7d4541462242113e16d2f53 100644
+--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
++++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+@@ -544,6 +544,11 @@ public final class CraftMagicNumbers implements UnsafeValues {
+     public io.papermc.paper.inventory.ItemRarity getItemStackRarity(org.bukkit.inventory.ItemStack itemStack) {
+         return io.papermc.paper.inventory.ItemRarity.values()[getItem(itemStack.getType()).getRarity(CraftItemStack.asNMSCopy(itemStack)).ordinal()];
+     }
++
++    @Override
++    public int getProtocolVersion() {
++        return net.minecraft.SharedConstants.getCurrentVersion().getProtocolVersion();
++    }
+     // Paper end
+ 
+     /**