fix: Fix dremio dialect not having a `driver` field (#15198)

* Update __init__.py

* Update superset/db_engine_specs/__init__.py

Co-authored-by: Beto Dealmeida <roberto@dealmeida.net>

Co-authored-by: Beto Dealmeida <roberto@dealmeida.net>

superset/db_engine_specs/__init__.py

@@ -121,7 +121,7 @@ def get_available_engine_specs() -> Dict[Type[BaseEngineSpec], Set[str]]:
         except Exception:  # pylint: disable=broad-except
             logger.warning("Unable to load SQLAlchemy dialect: %s", dialect)
         else:
-            drivers[dialect.name].add(dialect.driver)
+            drivers[dialect.name].add(getattr(dialect, "driver", dialect.name))
 
     engine_specs = get_engine_specs()
     return {