fix: broken SQL statement in wallet db_set_utxo

I discovered this accidentally when using the `tests/plugins/dblog.py`
plugin on another testcase: tests/test_connection.py::test_fail_unconfirmed

There the plugin/hook crashes because it can't execute the statement:
```json
{
  "jsonrpc": "2.0",
  "id": 34,
  "error": {
    "code": -32600,
    "message": "Error while processing db_write: unrecognized token: \"174WHERE\"",
    "traceback": "Traceback (most recent call last):\n  File \"/home/will/projects/lightning.git/contrib/pyln-client/pyln/client/plugin.py\", line 535, in _dispatch_request\n    result = self._exec_func(method.func, request)\n  File \"/home/will/projects/lightning.git/contrib/pyln-client/pyln/client/plugin.py\", line 520, in _exec_func\n    return func(*ba.args, **ba.kwargs)\n  File \"/home/will/projects/lightning.git/tests/plugins/dblog.py\", line 45, in db_write\n    plugin.conn.execute(c)\nsqlite3.OperationalError: unrecognized token: \"174WHERE\"\n"
  }
}
```

Changelog-Fixed: broken SQL statement in sb_set_utxo

wallet/wallet.c

@@ -414,7 +414,7 @@ static void db_set_utxo(struct db *db, const struct utxo *utxo)
 		assert(!utxo->reserved_til);
 
 	stmt = db_prepare_v2(
-		db, SQL("UPDATE outputs SET status=?, reserved_til=?"
+		db, SQL("UPDATE outputs SET status=?, reserved_til=? "
 			"WHERE prev_out_tx=? AND prev_out_index=?"));
 	db_bind_int(stmt, 0, output_status_in_db(utxo->status));
 	db_bind_int(stmt, 1, utxo->reserved_til);