Fix typo (#19160)

packages/flutter/lib/src/rendering/performance_overlay.dart

@@ -44,14 +44,14 @@ enum PerformanceOverlayOption {
 
 /// Displays performance statistics.
 ///
-/// The overlay show two time series. The first shows how much time was required
-/// on this thread to produce each frame. The second shows how much time was
-/// required on the GPU thread to produce each frame. Ideally, both these values
-/// would be less than the total frame budget for the hardware on which the app
-/// is running. For example, if the hardware has a screen that updates at 60 Hz,
-/// each thread should ideally spend less than 16ms producing each frame. This
-/// ideal condition is indicated by a green vertical line for each thread.
-/// Otherwise, the performance overlay shows a red vertical line.
+/// The overlay shows two time series. The first shows how much time was
+/// required on this thread to produce each frame. The second shows how much
+/// time was required on the GPU thread to produce each frame. Ideally, both
+/// these values would be less than the total frame budget for the hardware on
+/// which the app is running. For example, if the hardware has a screen that
+/// updates at 60 Hz, each thread should ideally spend less than 16ms producing
+/// each frame. This ideal condition is indicated by a green vertical line for
+/// each thread. Otherwise, the performance overlay shows a red vertical line.
 ///
 /// The simplest way to show the performance overlay is to set
 /// [MaterialApp.showPerformanceOverlay] or [WidgetsApp.showPerformanceOverlay]