docs: fix typos and update https references (#8154)

Co-authored-by: Tim Lai <timothy.lai@smartbear.com>

docs/customization/overview.md

@@ -7,7 +7,7 @@ Swagger UI leans heavily on concepts and patterns found in React and Redux.
 If you aren't already familiar, here's some suggested reading:
 
 - [React: Quick Start (reactjs.org)](https://reactjs.org/docs/hello-world.html)
-- [Redux README (redux.js.org)](http://redux.js.org/)
+- [Redux README (redux.js.org)](https://redux.js.org/)
 
 In the following documentation, we won't take the time to define the fundamentals covered in the resources above.
 

docs/customization/plugin-api.md

@@ -100,7 +100,7 @@ The Action interface enables the creation of new Redux action creators within a
 
 This action creator function will be exposed to container components as `exampleActions.updateFavoriteColor`. When this action creator is called, the return value (which should be a [Flux Standard Action](https://github.com/acdlite/flux-standard-action)) will be passed to the `example` reducer, which we'll define in the next section.
 
-For more information about the concept of actions in Redux, see the [Redux Actions documentation](http://redux.js.org/docs/basics/Actions.html).
+For more information about the concept of actions in Redux, see the [Redux Actions documentation](https://redux.js.org/tutorials/fundamentals/part-2-concepts-data-flow#actions).
 
 #### Reducers