Update NuGet dependencies

[martincostello]

• Bump xunit from 2.4.1 to 2.6.6 to resolve https://github.com/domaindrivendev/Swashbuckle.AspNetCore/security/dependabot/25 and https://github.com/domaindrivendev/Swashbuckle.AspNetCore/security/dependabot/26.
• Bump Microsoft.AspNetCore.Mvc.Testing to resolve https://github.com/domaindrivendev/Swashbuckle.AspNetCore/security/dependabot/27 and https://github.com/domaindrivendev/Swashbuckle.AspNetCore/security/dependabot/28.
• Bump test dependencies to latest versions for .NET 8.0.18 and 9.0.7.

[Copilot]

Pull Request Overview

This PR updates NuGet dependencies to address security vulnerabilities and bump test dependencies to their latest versions. The changes focus on upgrading xunit from 2.4.1 to 2.6.6 and updating Microsoft.AspNetCore.Mvc.Testing, along with other related dependencies for both .NET 8.0.18 and 9.0.7.

• Update xunit from 2.4.1 to 2.6.6 to resolve security vulnerabilities
• Bump Microsoft.AspNetCore.Mvc.Testing and related testing packages to latest versions
• Update .NET 8.0 dependencies from 8.0.17 to 8.0.18 and .NET 9.0 dependencies from 9.0.6 to 9.0.7

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/WebSites/WebApi/WebApi.csproj	Updates Microsoft.AspNetCore.OpenApi to 9.0.7 for .NET 9.0 compatibility
test/WebSites/OAuth2Integration/OAuth2Integration.csproj	Updates Microsoft.AspNetCore.Authentication.JwtBearer to 8.0.18 and 9.0.7 for respective frameworks
test/WebSites/MvcWithNullable/MvcWithNullable.csproj	Updates Microsoft.AspNetCore.OpenApi to 9.0.7 for .NET 9.0 compatibility
test/Swashbuckle.AspNetCore.IntegrationTests/Swashbuckle.AspNetCore.IntegrationTests.csproj	Updates testing packages (Microsoft.AspNetCore.Mvc.Testing and TestHost) to 8.0.18 and 9.0.7
src/Swashbuckle.AspNetCore.ApiTesting/Swashbuckle.AspNetCore.ApiTesting.csproj	Updates Microsoft.AspNetCore.Mvc.Testing to 8.0.5 for .NET 8.0
src/Swashbuckle.AspNetCore.ApiTesting.Xunit/Swashbuckle.AspNetCore.ApiTesting.Xunit.csproj	Updates xunit from 2.4.1 to 2.6.6
Directory.Packages.props	Updates central package versions for Microsoft.AspNetCore dependencies to 8.0.18

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.28%. Comparing base (1c56ec4) to head (87e4c70).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3513   +/-   ##
=======================================
  Coverage   94.28%   94.28%           
=======================================
  Files         110      110           
  Lines        3816     3816           
  Branches      722      722           
=======================================
  Hits         3598     3598           
  Misses        218      218           

Flag	Coverage Δ
Linux	94.28% <ø> (ø)
Windows	94.28% <ø> (ø)
macOS	94.28% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

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

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.