Changed regex to avoid false positives

Current regex falsely triggered for a such string:
```
*** Assertion failure in -[UICollectionView _endItemAnimations], /SourceCache/UIKit_Sim/UIKit-2903.23/UICollectionView.m:3716
```
It matches a full string, while the new one matches only file path(`/SourceCache/UIKit_Sim/UIKit-2903.23/UICollectionView.m:3716`).
See links below:

Before: http://regexr.com/?38jid
After: http://regexr.com/?38jig