Remove unnecessary platform check. (#7564)

This isn't actually needed since the class won't be available on platforms it doesn't support.

Author: ryanwilson

FirebaseCore/Sources/FIRApp.m

@@ -346,7 +346,6 @@ - (BOOL)configureCore {
     return NO;
   }
 
-#if TARGET_OS_IOS
   // Initialize the Analytics once there is a valid options under default app. Analytics should
   // always initialize first by itself before the other SDKs.
   if ([self.name isEqualToString:kFIRDefaultAppName]) {
@@ -367,7 +366,6 @@ - (BOOL)configureCore {
       }
     }
   }
-#endif
 
   [self subscribeForAppDidBecomeActiveNotifications];