Fix Rename adornment positioning after scrolling (#79303)

When Rename is invoked after scrolling up, the adornment is occasionally
displayed misplaced out of viewport. See
https://developercommunity.visualstudio.com/t/Rename-dialog-opens-up-outside-of-editor/10919621.


This is a regression from #77466, which was a fix for horizontal
clipping but also changed vertical positioning to never be negative.
Unfortunately, when scrolling up, text view's viewport top and bottom
can be negative.
The fix is to remove unnecessary Math.Max on top position value.

Author: dibarbet

src/EditorFeatures/Core.Wpf/InlineRename/UI/Adornment/RenameFlyout.xaml.cs

@@ -152,7 +152,8 @@ private void PositionAdornment()
             MaxWidth = _textView.ViewportRight;
             MinWidth = Math.Min(DefaultMinWidth, _textView.ViewportWidth);
 
-            Canvas.SetTop(this, Math.Max(0, top));
+            // Top can be negative if the viewport is scrolled up, but not left
+            Canvas.SetTop(this, top);
             Canvas.SetLeft(this, Math.Max(0, left));
         }