[CP-stable]fix reorderable_list_test.dart (#164050)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)
Please fill in the form below, and a flutter domain expert will evaluate this cherry pick request.

### Issue Link:
What is the link to the issue this cherry-pick is addressing? 

https://github.com/flutter/flutter/issues/164128

### Changelog Description:
Explain this cherry pick in one line that is accessible to most Flutter developers. See [best practices](https://github.com/flutter/flutter/blob/main/docs/releases/Hotfix-Documentation-Best-Practices.md) for examples

This cherry pick lands a fix to a test that is currently causing all presubmits to fail on the 3.29-candidate.0 stable release branch. The failure fixed in this test is dependent on the random ordering seed, which is why it didn't fail before. The current seed in which it fails is `--test-randomize-ordering-seed=20250221`.

### Impact Description:
What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)? Does it impact development (ex. flutter doctor crashes when Android Studio is installed), or the shipping production app (the app crashes on launch)

The only change is to reduce the flakiness of reorderable_list.test.dart.

### Workaround:
Is there a workaround for this issue?

Change the seed?

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

```
 flutter test /Users/jmccandless/Projects/flutter/packages/flutter/test/material/reorderable_list_test.dart --test-randomize-ordering-seed=20250221
```