Removed empty methods

Summary:
Issue fixed: #

- [x] All tests pass. Demo project builds and runs.
- [ ] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes #945

Differential Revision: D5881110

Pulled By: rnystrom

fbshipit-source-id: 7f20fcaac04f64576a52ca68af87d3db64f199b9

Examples/Examples-iOS/IGListKitExamples/SectionControllers/MonthSectionController.swift

@@ -95,6 +95,4 @@ final class MonthSectionController: ListBindingSectionController<ListDiffable>,
         update(animated: true)
     }
 
-    func sectionController(_ sectionController: ListBindingSectionController<ListDiffable>, didDeselectItemAt index: Int, viewModel: Any) {}
-
 }

Examples/Examples-tvOS/IGListKitExamples/SectionControllers/CarouselSectionController.swift

@@ -52,6 +52,4 @@ final class CarouselSectionController: ListSectionController {
         number = object as? Int
     }
 
-    override func didSelectItem(at index: Int) {}
-
 }

Examples/Examples-tvOS/IGListKitExamples/SectionControllers/HorizontalSectionController.swift

@@ -53,8 +53,6 @@ final class HorizontalSectionController: ListSectionController, ListAdapterDataS
         number = object as? Int
     }
 
-    override func didSelectItem(at index: Int) {}
-
     // MARK: ListAdapterDataSource
 
     func objects(for listAdapter: ListAdapter) -> [ListDiffable] {

Examples/Examples-tvOS/IGListKitExamples/SectionControllers/LabelSectionController.swift

@@ -39,6 +39,4 @@ final class LabelSectionController: ListSectionController {
         self.object = String(describing: object)
     }
 
-    override func didSelectItem(at index: Int) {}
-
 }