Fix another case of concurrency issue in data fixers

Spigot-Server-Patches/Fix-concurrency-issues-in-DataFixers.patch

@@ -12,9 +12,18 @@ be synchronized to be safe for use over multiple threads.
 There may be more cases, but these are extremely obvious ones.
 
 diff --git a/src/main/java/com/mojang/datafixers/DataFixerUpper.java b/src/main/java/com/mojang/datafixers/DataFixerUpper.java
-index fb2c380f8a..9299cbbdbd 100644
+index fb2c380f8a..c8e7a8aa10 100644
 --- a/src/main/java/com/mojang/datafixers/DataFixerUpper.java
 +++ b/src/main/java/com/mojang/datafixers/DataFixerUpper.java
+@@ -0,0 +0,0 @@ public class DataFixerUpper implements DataFixer {
+     private final Int2ObjectSortedMap<Schema> schemas;
+     private final List<DataFix> globalList;
+     private final IntSortedSet fixerVersions;
+-    private final Long2ObjectMap<TypeRewriteRule> rules = new Long2ObjectOpenHashMap<>();
++    private final Long2ObjectMap<TypeRewriteRule> rules = it.unimi.dsi.fastutil.longs.Long2ObjectMaps.synchronize(new Long2ObjectOpenHashMap<>()); // Paper
+ 
+     protected DataFixerUpper(final Int2ObjectSortedMap<Schema> schemas, final List<DataFix> globalList, final IntSortedSet fixerVersions) {
+         this.schemas = schemas;
 @@ -0,0 +0,0 @@ public class DataFixerUpper implements DataFixer {
          final int expandedDataVersion = DataFixUtils.makeKey(dataVersion);