Simplify & optimise BurningManAccountingStore.purgeLastTenBlocks

Remove the last 10 blocks one-by-one from the end of the internal linked
list of blocks, instead of rebuilding a truncated list from scratch.
(This all takes place within a write-lock anyway, so it's atomic.)

core/src/main/java/bisq/core/dao/burningman/accounting/storage/BurningManAccountingStore.java

@@ -74,7 +74,9 @@ public void purgeLastTenBlocks() {
         Lock writeLock = readWriteLock.writeLock();
         writeLock.lock();
         try {
-            purgeLast10Blocks();
+            for (int i = 0; i < 10 && !blocks.isEmpty(); i++) {
+                blocks.removeLast();
+            }
         } finally {
             writeLock.unlock();
         }
@@ -147,17 +149,6 @@ private void tryToAddNewBlock(AccountingBlock newBlock) throws BlockHeightNotCon
         }
     }
 
-    private void purgeLast10Blocks() {
-        if (blocks.size() <= 10) {
-            blocks.clear();
-            return;
-        }
-
-        List<AccountingBlock> purged = new ArrayList<>(blocks.subList(0, blocks.size() - 10));
-        blocks.clear();
-        blocks.addAll(purged);
-    }
-
     public Message toProtoMessage() {
         List<AccountingBlock> blocksCopy;
         Lock readLock = readWriteLock.readLock();