[v2][iOS] Simplify searchBarHiddenWhenScrolling making its behaviour default to iOS one (#3611)

* Simplify searchBarHiddenWhenScrolling making its behaviour default to iOS one

* Update RNNTopBarOptions.m

lib/ios/RNNRootViewController.m

 -(void)viewDidAppear:(BOOL)animated {
 	[super viewDidAppear:animated];
 	[self.eventEmitter sendComponentDidAppear:self.componentId componentName:self.componentName];
-	if (@available(iOS 11.0, *)) {
-		if (self.navigationItem.searchController && [self.options.topBar.searchBarHiddenWhenScrolling boolValue]) {
-			self.navigationItem.hidesSearchBarWhenScrolling = YES;
-		}
-	}
 }
 
 - (void)viewWillDisappear:(BOOL)animated {

lib/ios/RNNTopBarOptions.m

 				search.searchBar.placeholder = self.searchBarPlaceholder;
 			}
 			viewController.navigationItem.searchController = search;
-			// enable it back if needed on componentDidAppear
-			viewController.navigationItem.hidesSearchBarWhenScrolling = NO;
+			
+			viewController.navigationItem.hidesSearchBarWhenScrolling = [self.searchBarHiddenWhenScrolling boolValue];
 			
 			// Fixes #3450, otherwise, UIKit will infer the presentation context to be the root most view controller
 			viewController.definesPresentationContext = YES;