script/checktrie: fix the import to SQLDB

This is nothing special, it just allows the module
to run without throwing an error.

From
```
from lbry.wallet.server.db import SQLDB
```

To
```
from lbry.wallet.server.db.writer import SQLDB
```

scripts/checktrie.py

@@ -2,7 +2,7 @@
 import asyncio
 from binascii import hexlify
 
-from lbry.wallet.server.db import SQLDB
+from lbry.wallet.server.db.writer import SQLDB
 from lbry.wallet.server.coin import LBC
 from lbry.wallet.server.daemon import Daemon