Fix outdated comment about overflow (#112595)

Author: Hixie

packages/flutter/lib/src/cupertino/refresh.dart

@@ -380,13 +380,13 @@ class CupertinoSliverRefreshControl extends StatefulWidget {
   ) {
     final double percentageComplete = clampDouble(pulledExtent / refreshTriggerPullDistance, 0.0, 1.0);
 
-    // Place the indicator at the top of the sliver that opens up. Note that we're using
-    // a Stack/Positioned widget because the CupertinoActivityIndicator does some internal
-    // translations based on the current size (which grows as the user drags) that makes
-    // Padding calculations difficult. Rather than be reliant on the internal implementation
-    // of the activity indicator, the Positioned widget allows us to be explicit where the
-    // widget gets placed. Also note that the indicator should appear over the top of the
-    // dragged widget, hence the use of Overflow.visible.
+    // Place the indicator at the top of the sliver that opens up. We're using a
+    // Stack/Positioned widget because the CupertinoActivityIndicator does some
+    // internal translations based on the current size (which grows as the user drags)
+    // that makes Padding calculations difficult. Rather than be reliant on the
+    // internal implementation of the activity indicator, the Positioned widget allows
+    // us to be explicit where the widget gets placed. The indicator should appear
+    // over the top of the dragged widget, hence the use of Clip.none.
     return Center(
       child: Stack(
         clipBehavior: Clip.none,