Unstable unit test: System.Windows.Forms.Tests.ToolStripTests.ToolStrip_WndProc_InvokeMouseActivateWithHandle_Success

Related #11227

### Test

System.Windows.Forms.Tests.ToolStripTests.ToolStrip_WndProc_InvokeMouseActivateWithHandle_Success

### Issue description

**The case failed in X64 and X86 unit tests, the failure link:**

- [#20240501.11 • Update branding to 6.0.31 (#11302)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=662561&view=ms.vss-test-web.build-test-results-tab&runId=16425146&resultId=107698&paneView=debug)
- [#20240513.6 • [main] Update dependencies from dotnet/runtime (#11364)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=673968&view=ms.vss-test-web.build-test-results-tab&runId=16709506&resultId=111929&paneView=debug)

**Error Message:**
- Assert.Equal() Failure
Expected: 0
Actual: 2

**Stack trace:**
```
at System.Windows.Forms.Tests.ToolStripTests.ToolStrip_WndProc_InvokeMouseActivateWithHandle_Success()
in /_/src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ToolStripTests.cs:line 7169
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
```