test(logs): add Assertion for sentry.origin for MAUI

[Flash0ver]

During #4699 and #4700 I noticed that we were missing one assertion.

This is a follow-up to #4566.
In particular to keep SentryMauiStructuredLoggerProviderTests.cs in sync with:

sentry-dotnet/test/Sentry.AspNetCore.Tests/SentryAspNetCoreStructuredLoggerProviderTests.cs

Lines 95 to 96 in 18ca31b

	capturedLog.TryGetAttribute("sentry.origin", out object? origin).Should().BeTrue();
	origin.Should().Be("auto.log.extensions_logging");

---

#skip-changelog

[Flash0ver]

@sentry review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (version6@19a8c1a). Learn more about missing BASE report.

Additional details and impacted files

@@             Coverage Diff             @@
##             version6    #4701   +/-   ##
===========================================
  Coverage            ?   73.17%           
===========================================
  Files               ?      480           
  Lines               ?    17422           
  Branches            ?     3437           
===========================================
  Hits                ?    12749           
  Misses              ?     3822           
  Partials            ?      851           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[alexsohn1126]

Looks good!