fix TalkBack announcing wrong first item

talkback would allways use last column item as first item

REGRESSION: If we scroll to the last page, without doing a full page
scroll but a partial page scroll. TalkBack announces showing items 19 to
21 while it should be 19 to 29.
I believe the issue is in getScrollDelta not detecting this partial
scroll of the page.

https://user-images.githubusercontent.com/24992535/154172356-6a8f7ebc-cfd9-4c5c-80aa-1092ccc6b609.mp4

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -176,6 +176,9 @@ public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event)
                       if (nestedChildAccessibilityInfo != null) {
                         accessibilityCollectionItemInfo = nestedChildAccessibilityInfo;
                       }
+                      if (firstVisibleIndex == null) {
+                        firstVisibleIndex = accessibilityCollectionItemInfo.getInt("itemIndex");
+                      }
                     }
                   }
                 }