Update _vars.py

Fix the sql OperationalError ocurring due to the invalid DATABASE_CONN_STRING protocol's `/` amount

dooit/api/_vars.py

@@ -3,6 +3,6 @@
 
 ROOT_FOLDER = Path(user_data_dir("dooit"))
 DATABASE_FILE = ROOT_FOLDER / "dooit.db"
-DATABASE_CONN_STRING = f"sqlite:////{DATABASE_FILE}"
+DATABASE_CONN_STRING = f"sqlite:///{DATABASE_FILE}"
 
 DATABASE_FILE.parent.mkdir(parents=True, exist_ok=True)