Fixing overscrolling issue on Virtualized List (#23181)

Summary:
Changelog:
----------
[iOS][fixed] Fixed overscroll behavior on iOS virtualized lists (Fixes #18098)
Pull Request resolved: https://github.com/facebook/react-native/pull/23181

Differential Revision: D13838579

Pulled By: cpojer

fbshipit-source-id: 2ec5787218ecca0e01aaf31bfbb7d630cf9f1f09

Libraries/Lists/VirtualizedList.js

@@ -330,13 +330,20 @@ class VirtualizedList extends React.PureComponent<Props, State> {
       return;
     }
     const frame = this._getFrameMetricsApprox(index);
-    const offset =
+    const maxScroll =
+      this._scrollMetrics.contentLength - this._scrollMetrics.visibleLength;
+    let offset =
       Math.max(
         0,
         frame.offset -
           (viewPosition || 0) *
             (this._scrollMetrics.visibleLength - frame.length),
       ) - (viewOffset || 0);
+
+    /* Fix for overscrolling */
+    if (offset > maxScroll) {
+      offset = maxScroll;
+    }
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