Fix setting the contentOffset value when refresh ends (#24191)

Summary:
It closes #24170.
I opened the issue yesterday, and I think I found the way how to resolve it. So, I'm opening this PR directly without any comment on the issue.

In the `endRefreshProgrammatically` of `RCTRefreshControl.m`, the comment says that " The contentOffset of the scrollview MUST be greater than 0". However, if the `contentInset` prop is set for the `FlatList`, I think `contentOffset` can be a negative value after refreshing and should be greater than `-contentInset.top`.

As I reported the bug in that issue, If I am using `contentInset` prop to the `FlatList`, making `contentOffset` value be always 0 when refreshing ends causes something wrong situation.

[iOS] [Fixed] - Fix setting the contnetOffset when refreshing ends
Pull Request resolved: https://github.com/facebook/react-native/pull/24191

Differential Revision: D14710987

Pulled By: sahrens

fbshipit-source-id: 03f06df9a93a2a46a7cc0b56269091778805917e

React/Views/RCTRefreshControl.m

@@ -76,12 +76,12 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
 - (void)endRefreshingProgrammatically
 {
-  // The contentOffset of the scrollview MUST be greater than 0 before calling
+  // The contentOffset of the scrollview MUST be greater than the contentInset before calling
   // endRefreshing otherwise the next pull to refresh will not work properly.
   UIScrollView *scrollView = (UIScrollView *)self.superview;
-  if (_refreshingProgrammatically && scrollView.contentOffset.y < 0) {
+  if (_refreshingProgrammatically && scrollView.contentOffset.y < -scrollView.contentInset.top) {
     UInt64 endRefreshingTimestamp = _currentRefreshingStateTimestamp;
-    CGPoint offset = {scrollView.contentOffset.x, 0};
+    CGPoint offset = {scrollView.contentOffset.x, -scrollView.contentInset.top};
     [UIView animateWithDuration:0.25
                           delay:0
                         options:UIViewAnimationOptionBeginFromCurrentState