Increase delay for checking integration_ui_keyboard_resize test success (#141301)

Increases delay for checking keyboard resizing to potentially accommodate the occasional longer delay of the Pixel 7 Pro.

Intended to address https://github.com/flutter/flutter/issues/140645.

dev/integration_tests/ui/test_driver/keyboard_resize_test.dart

@@ -32,7 +32,7 @@ void main() {
       await driver.tap(defaultTextField);
 
       bool heightTextDidShrink = false;
-      for (int i = 0; i < 3; ++i) {
+      for (int i = 0; i < 6; ++i) {
         await Future<void>.delayed(const Duration(seconds: 1));
         // Measure the height with keyboard displayed.
         final String heightWithKeyboardShown = await driver.getText(heightText);