fix: use proper timestamp in frameElapsed calculation (#26114)

Summary:
Fix a bug where `CACurrentMediaTime` was being used to calculate the elapsed frame time, even though it's not comparable to `NSDate.timeIntervalSince1970` time.

## Changelog

[iOS] [Fixed] - callIdleCallbacks deadline calculation
Pull Request resolved: #26114

Test Plan: None

Differential Revision: D17314125

Pulled By: cpojer

fbshipit-source-id: 5061a3954371df2134f0c77dc260228668abe747

React/Modules/RCTTiming.m

@@ -268,9 +268,9 @@ - (void)didUpdateFrame:(RCTFrameUpdate *)update
   }
 
   if (_sendIdleEvents) {
-    NSTimeInterval frameElapsed = (CACurrentMediaTime() - update.timestamp);
+    NSTimeInterval currentTimestamp = [[NSDate date] timeIntervalSince1970];
+    NSTimeInterval frameElapsed = currentTimestamp - update.timestamp;
     if (kFrameDuration - frameElapsed >= kIdleCallbackFrameDeadline) {
-      NSTimeInterval currentTimestamp = [[NSDate date] timeIntervalSince1970];
       NSNumber *absoluteFrameStartMS = @((currentTimestamp - frameElapsed) * 1000);
       [_bridge enqueueJSCall:@"JSTimers"
                       method:@"callIdleCallbacks"