Fix duplicate test cases causing xUnit to skip tests (#456)

## Problem

When running tests with `dotnet test --settings
./build/targets/tests/test.runsettings`, xUnit was showing duplicate
test case warnings and skipping tests:

```
[xUnit.net] Skipping test case with duplicate ID '563efcecb5eb6234578552365c961e96245c2c02'
[xUnit.net] Skipping test case with duplicate ID '61d653fcc9ca0f6aacdb2092a69413258d3d7792'  
[xUnit.net] Skipping test case with duplicate ID '25a082fbf19ca8396f4c22db48a7c3f9937a65ae'
[xUnit.net] Skipping test case with duplicate ID '0b16ad785c3c66c94e28e8b5569b212a216a6fc2'
```

## Root Cause

The `CallbackSignatureShouldMatchMockedMethodCodeFixTests.TestData()`
method contained duplicate test cases on lines 95-102:

```csharp
[
    """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
    """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
],
[
    """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",  // DUPLICATE
    """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",  // DUPLICATE
],
```

When combined with the
`.WithNamespaces().WithMoqReferenceAssemblyGroups()` extension methods
that multiply each test case by:
- Namespace variations (empty string and "namespace MyNamespace;") 
- Moq versions (Net80WithOldMoq and Net80WithNewMoq)

This created 4 identical test case IDs, causing xUnit to skip the
duplicates.

## Solution

Removed one of the duplicate test case entries (lines 99-102), keeping
only the necessary test case.

## Verification

✅ **Before fix:** 4 duplicate test case warnings  
✅ **After fix:** No duplicate warnings, all 896 tests pass  
✅ **Minimal change:** Only 4 lines removed, 0 lines added  
✅ **Build and test successful with pedantic mode**

Fixes #455.

---

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---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: rjmurillo <6811113+rjmurillo@users.noreply.github.com>

Author: Copilot

tests/Moq.Analyzers.Test/CallbackSignatureShouldMatchMockedMethodCodeFixTests.cs

@@ -96,10 +96,6 @@ public static IEnumerable<object[]> TestData()
                 """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
                 """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
             ],
-            [
-                """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
-                """new Mock<IFoo>().Setup(m => m.Do((long)42)).Returns((long bar) => true);""",
-            ],
             [
                 """new Mock<IFoo>().Setup(m => m.Do(42)).Returns((object? bar) => true);""",
                 """new Mock<IFoo>().Setup(m => m.Do(42)).Returns((object? bar) => true);""",