Fix incorrect nullability annotation in BlockIgniteEvent constructor

By: Parker Hawke <hawkeboyz2@hotmail.com>

paper-api/src/main/java/org/bukkit/event/block/BlockIgniteEvent.java

@@ -21,7 +21,7 @@ public class BlockIgniteEvent extends BlockEvent implements Cancellable {
     private final Block ignitingBlock;
     private boolean cancel;
 
-    public BlockIgniteEvent(@NotNull final Block theBlock, @NotNull final IgniteCause cause, @NotNull final Entity ignitingEntity) {
+    public BlockIgniteEvent(@NotNull final Block theBlock, @NotNull final IgniteCause cause, @Nullable final Entity ignitingEntity) {
         this(theBlock, cause, ignitingEntity, null);
     }