Updated borderColor view property to UIColor (facebook#33176)

Summary:
In facebook@c974cbf I changed the borderColor from CGColor to UIColor. I missed this view property which should also be updated to reflect the original change.

## Changelog

[iOS] [Fixed] - Set RCTView borderColor to UIColor

Pull Request resolved: facebook#33176

Test Plan: Nothing to test. See PR facebook#29728

Reviewed By: javache

Differential Revision: D34461141

Pulled By: genkikondo

fbshipit-source-id: 51adf39c1cebe8e3b53285961358e4c7f26192db

React/Views/RCTViewManager.m

@@ -359,7 +359,7 @@ - (RCTShadowView *)shadowView
     view.layer.cornerRadius = json ? [RCTConvert CGFloat:json] : defaultView.layer.cornerRadius;
   }
 }
-RCT_CUSTOM_VIEW_PROPERTY(borderColor, CGColor, RCTView)
+RCT_CUSTOM_VIEW_PROPERTY(borderColor, UIColor, RCTView)
 {
   if ([view respondsToSelector:@selector(setBorderColor:)]) {
     view.borderColor = json ? [RCTConvert UIColor:json] : defaultView.borderColor;