Fixed assertion #trivial (Instagram#1203)

Summary:
Fixed the order of variables in this assertion.

- [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)
Pull Request resolved: Instagram#1203

Differential Revision: D8770959

Pulled By: rnystrom

fbshipit-source-id: 982996cc218d5db32a0fb67d045ac05870741d71

Source/Common/IGListDiff.mm

@@ -298,8 +298,8 @@ static id IGListDiffing(BOOL returnIndexPaths,
     }
 
     NSCAssert((oldCount + [mInserts count] - [mDeletes count]) == newCount,
-              @"Sanity check failed applying %li inserts and %lu deletes to old count %lu equaling new count %li",
-              (long)oldCount, (unsigned long)[mInserts count], (unsigned long)[mDeletes count], (long)newCount);
+              @"Sanity check failed applying %lu inserts and %lu deletes to old count %li equaling new count %li",
+              (unsigned long)[mInserts count], (unsigned long)[mDeletes count], (long)oldCount, (long)newCount);
 
     if (returnIndexPaths) {
         return [[IGListIndexPathResult alloc] initWithInserts:mInserts