Fix "new file header template" whitespace #trivial (#1324)

Summary:
* Removing an extra new line
* Trailing whitespace

![image](https://user-images.githubusercontent.com/5719/58054482-b198cc00-7b28-11e9-8e9d-ddcfb2bb0e86.png)

## Changes in this pull request

Issue fixed: #984

### Checklist

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] 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: #1324

Differential Revision: D15424844

fbshipit-source-id: c5f10932149873df95e0d748ca088da917501773

IGListKit.xcworkspace/xcshareddata/IDETemplateMacros.plist

@@ -3,7 +3,7 @@
 <plist version="1.0">
 <dict>
 <key>FILEHEADER</key>
-<string> 
+<string>
 // Copyright (c) Facebook, Inc. and its affiliates.
 // All rights reserved.
 //
@@ -13,10 +13,9 @@
 //
 // GitHub:
 // https://github.com/Instagram/IGListKit
-// 
+//
 // Documentation:
 // https://instagram.github.io/IGListKit/
-//
-</string>
+//</string>
 </dict>
 </plist>