I think that’s perfectly fine. There is no place to states that Actions and Reducers have a 1:1 mapping. In fact, creator of Redux explicitly says that there is no relation between them, many reducers can react to a single actions, a single reducer can react to multiple actions.
I think he says it best: https://github.com/reduxible/reduxible/issues/8
Tweet: https://twitter.com/dan_abramov/status/691608868628119552
Relevant SO: Redux: Why not put actions and reducer in same file?