Update test method to fix test issue:47861

[SimonZhao888]

Fix test issue: #47861

Root Cause

Throw an exception in the action delegate will stop the Retry method!
Referring to the ExecuteAsyncWithRetry method

public static async Task<T> ExecuteAsyncWithRetry<T>(Func<Task<T>> action,
    Func<T, bool> shouldStopRetry,
    int maxRetryCount,
    Func<IEnumerable<Task>> timer,
    string taskDescription = "")
{
    var count = 0;
    foreach (var t in timer())
    {
        await t;
        T result = default;
        count++;

        result = await action();

        if (shouldStopRetry(result))
        {
            return result;
        }

        if (count == maxRetryCount)
        {
            return result;
        }
    }
    throw new Exception("Timer should not be exhausted");
}

Whether or not to retry is only relevant to the expression in

await ExecuteAsyncWithRetry(action, result => result != null && !result.Equals(default), maxRetryCount, timer);

so consider modifying the test case to simulate failure retries.

Proposed changes

• Update test case.

[Copilot]

Pull Request Overview

This PR updates the ItRetriesOnError test in GivenExponentialRetry.cs to simulate retry behavior via null results rather than thrown exceptions, and re-enables the test by removing its Skip attribute.

• Removed the [Fact(Skip = ...)] attribute to run the test.
• Changed the test action to return null instead of throwing an exception.
• Updated assertions to expect a null result and verify retry count.

Comments suppressed due to low confidence (1)

test/dotnet.Tests/GivenExponentialRetry.cs:29

• [nitpick] The test name 'ItRetriesOnError' suggests exception-based failures, but the updated test simulates a null result. Consider renaming it to something like 'ItRetriesOnNullResult' to better reflect its behavior.

        public async Task ItRetriesOnError()