fix(iOS): remove leftover _sheetsScrollView reference after cherry-pi…

…cking from main (#2447)

## Description

This PR fixes iOS build after recent cherry-picks. It removes the
_sheetsScrollView leftover reference.

## Checklist

- [ ] Ensured that CI passes

ios/RNSScreen.mm

@@ -620,7 +620,6 @@ - (BOOL)isTransparentModal
 - (void)invalidate
 {
   _controller = nil;
-  [_sheetsScrollView removeObserver:self forKeyPath:@"bounds" context:nil];
 }
 
 #if !TARGET_OS_TV && !TARGET_OS_VISION