Added missing header to umbrella header

Summary: Added FBWeakFramework+ApplePrivateFrameworks.h to umbrella header

Reviewed By: phyllipecesar

Differential Revision: D3126190

fb-gh-sync-id: 0373f07e0ad3a77a03897c7a691b4abbb7ba8b5b
fbshipit-source-id: 0373f07e0ad3a77a03897c7a691b4abbb7ba8b5b

FBControlCore/FBControlCore.h

@@ -31,5 +31,6 @@
 #import <FBControlCore/FBTaskExecutor.h>
 #import <FBControlCore/FBTerminationHandle.h>
 #import <FBControlCore/FBWeakFrameworkLoader.h>
+#import <FBControlCore/FBWeakFramework+ApplePrivateFrameworks.h>
 #import <FBControlCore/NSPredicate+FBControlCore.h>
 #import <FBControlCore/NSRunLoop+FBControlCore.h>