Fix Twitter handles in Example project

Summary:
I was exploring the example project when I noticed that two Twitter handles were wrong.
This will probably be the most useless PR ever in `IGListKit`, but it's good that you guys get the correct acknowledgment for your hard work! 🤓

- [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 have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/54

Reviewed By: ryanolsonk

Differential Revision: D4008615

Pulled By: rnystrom

fbshipit-source-id: 904892d40fed73045e724cc87dddf641af02e27d

Example/IGListKitExamples/ViewControllers/MixedDataViewController.swift

@@ -25,12 +25,12 @@ class MixedDataViewController: UIViewController, IGListAdapterDataSource {
     let data = [
         "Maecenas faucibus mollis interdum. Duis mollis, est non commodo luctus, nisi erat porttitor ligula, eget lacinia odio sem nec elit.",
         GridItem(color: UIColor(red: 237/255.0, green: 73/255.0, blue: 86/255.0, alpha: 1), itemCount: 6),
-        User(pk: 2, name: "Ryan Olson", handle: "jessie_squires"),
+        User(pk: 2, name: "Ryan Olson", handle: "ryanolsonk"),
         "Praesent commodo cursus magna, vel scelerisque nisl consectetur et.",
         User(pk: 4, name: "Oliver Rickard", handle: "ocrickard"),
         GridItem(color: UIColor(red: 56/255.0, green: 151/255.0, blue: 240/255.0, alpha: 1), itemCount: 5),
         "Nullam quis risus eget urna mollis ornare vel eu leo. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.",
-        User(pk: 3, name: "Jessie Squires", handle: "ryanolson"),
+        User(pk: 3, name: "Jessie Squires", handle: "jesse_squires"),
         GridItem(color: UIColor(red: 112/255.0, green: 192/255.0, blue: 80/255.0, alpha: 1), itemCount: 3),
         "Fusce dapibus, tellus ac cursus commodo, tortor mauris condimentum nibh, ut fermentum massa justo sit amet risus.",
         GridItem(color: UIColor(red: 163/255.0, green: 42/255.0, blue: 186/255.0, alpha: 1), itemCount: 7),