adapt annotations for SQLAlchemy 2.x

It is not possible to produce type annotations that work with both
versions 1.4 and 2.0. So keep to the principle of only supporting
newest versions when it comes to mypy. This means that some types
may have to be string quoted to not cause issues when running with
SQLAlchemy 1.4.

nominatim/api/connection.py

@@ -37,7 +37,7 @@ class SearchConnection:
 
     async def execute(self, sql: sa.sql.base.Executable,
                       params: Union[Mapping[str, Any], Sequence[Mapping[str, Any]], None] = None
-                     ) -> sa.engine.Result:
+                     ) -> 'sa.engine.Result[Any]':
         """ Execute a 'execute()' query on the connection.
         """
         return await self.connection.execute(sql, params)