Fix content rect calculation in SelectionManager

Fix a typo in `SelectionManager.getContentRect()` that results in
an invalid rect being calculated, causing text toolbar to not show
under certain conditions.

Fixes: b/332782845
Test: manual
Change-Id: I153b99f4146d870182af2898d9a675ed6ffa15e4

diff --git a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/SelectionManager.kt b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/SelectionManager.kt
index e18450f..c01b952 100644
--- a/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/SelectionManager.kt
+++ b/compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/text/selection/SelectionManager.kt

@@ -553,7 +553,7 @@
         if (visibleRect.width < 0 || visibleRect.height < 0) return null
 
         val rootRect = visibleRect.translate(containerCoordinates.positionInRoot())
-        return rootRect.copy(bottom = visibleRect.bottom + HandleHeight.value * 4)
+        return rootRect.copy(bottom = rootRect.bottom + HandleHeight.value * 4)
     }
 
     // This is for PressGestureDetector to cancel the selection.