add rollback tx at GetVoteOnHash #8637 (#8660)

At `turbo/jsonrpc/bor_snapshot.go:239` creates read only transaction and
acquire semaphore but does not rollback or commit transaction and
unrelease semaphore lock. Over time, this will result in the locking all
of semaphore resources. Any other resources can't acquire semaphore.

I added defer function to rollback transaction to release semaphore.

turbo/jsonrpc/bor_snapshot.go

@@ -241,6 +241,7 @@ func (api *BorImpl) GetVoteOnHash(ctx context.Context, starBlockNr uint64, endBl
 	if err != nil {
 		return false, err
 	}
+	defer tx.Rollback()
 
 	service := whitelist.GetWhitelistingService()