Debug only code were leaking into release builds on iOS. (#21232)

Summary:
RCT_DEBUG is always defined - it is just rather 0 or 1 so
```#ifndef RCT_DEBUG is always true```
Pull Request resolved: https://github.com/facebook/react-native/pull/21232

Differential Revision: D9982316

Pulled By: hramos

fbshipit-source-id: 5408bfcf95a6ed2beae38217a6ad1ee43950857d

React/Base/RCTUtils.m

@@ -810,7 +810,7 @@ static void RCTGetRGBAColorComponents(CGColorRef color, CGFloat rgba[4])
     default:
     {
 
-#ifdef RCT_DEBUG
+#if RCT_DEBUG
       //unsupported format
       RCTLogError(@"Unsupported color model: %i", model);
 #endif

React/CxxBridge/RCTCxxBridge.mm

@@ -651,7 +651,7 @@ struct RCTInstanceCallback : public InstanceCallback {
   NSArray<RCTModuleData *> *moduleDataById = [self registerModulesForClasses:modules];
 
   if (lazilyDiscovered) {
-#ifdef RCT_DEBUG
+#if RCT_DEBUG
     // Lazily discovered modules do not require instantiation here,
     // as they are not allowed to have pre-instantiated instance
     // and must not require the main queue.