Remove references to removed files in pbxproj files (#1376)

Summary:
Pull Request resolved: #1376

Our [builds](https://travis-ci.org/Instagram/IGListKit) have been failing since `IGListStackedSectionController` was removed in [D17200801](D17200801)/[1355](#1355). The error message in our Travis logs points to something related to `IGListStackedSectionController` causing the error:

```
X  error: /Users/travis/build/Instagram/IGListKit/Source/Internal/IGListStackedSectionControllerInternal.h: No such file or directory

** BUILD FAILED **

The following build commands failed:
	CpHeader /Users/travis/build/Instagram/IGListKit/Source/Internal/IGListStackedSectionControllerInternal.h /Users/travis/Library/Developer/Xcode/DerivedData/IGListKitExamples-cfbxdbnpimeeplcoaiqrlyrrqjxn/Build/Products/Debug-iphonesimulator/IGListKit/IGListKit.framework/PrivateHeaders/IGListStackedSectionControllerInternal.h
(1 failure)
```

Pretty sure the issue here is that the `xcodeproj` files were not rebuilt after deleting these files, which meant they were pointing to files that no longer existed, which caused the build to fail. I was able to fix this issue by running our `setup.sh` script, which regenerated the `xcodeproj` files.

Reviewed By: bdotdub

Differential Revision: D18064465

fbshipit-source-id: d07586a99d4bbb9346bdda0752dbd613eb1b6d03