Fix typo in collection context docs

Summary:
Issue fixed: #

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] 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 Instagram#860

Differential Revision: D5442884

Pulled By: rnystrom

fbshipit-source-id: d94832993279b2bae6f57e28fd2ef297bf00e291

Source/IGListCollectionContext.h

@@ -17,7 +17,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 /**
  The collection context provides limited access to the collection-related information that
- section controllers need for operations like sizing, dequeuing cells, insterting, deleting, reloading, etc.
+ section controllers need for operations like sizing, dequeuing cells, inserting, deleting, reloading, etc.
  */
 NS_SWIFT_NAME(ListCollectionContext)
 @protocol IGListCollectionContext <NSObject>