Bump the dev-dependencies group in /tests with 2 updates

[dependabot]

Bumps the dev-dependencies group in /tests with 2 updates: xunit and xunit.runner.visualstudio.

Updates xunit from 2.5.0 to 2.6.0

Commits

• 6a07b95 v2.6.0
• 5a7297e #2806: Performance improvements in Assert.Equal (v2)
• a6b5cc4 Add net6.0 binary to xunit.assert
• abc1dd3 Update Microsoft.NETCore.App.Ref to 6.0
• 52b6638 Move CA1304 and CA1305 enablement to production code only (not test code)
• e139d77 Ensure all throws of NotImplementedException contain messages
• 8a84fdb Ensure all GetHashCode functions are implemented (#2804) (v2)
• c853205 Unit tests for #2803 (v2)
• 8ffe56a Unit tests for #2800 (v2)
• b2e660e Replace (most) concatenation and interpolation (in shipped code) with String....
• Additional commits viewable in compare view

Updates xunit.runner.visualstudio from 2.5.0 to 2.5.3

Commits

• 6b60a9e v2.5.3
• 48d5ef6 Add diagnostic messages around DiaSession failures
• 32b7c99 Incorrect URL for Git repository in .nuspec file
• ce0f849 Bump up to v2.5.3-pre
• b56611b v2.5.2
• 9b843e1 Add Microsoft.TestPlatform.ObjectModel as a dependency in the nuspec for .NET...
• 9d28006 Add /.vscode/tasks.json for builds inside VS Code
• af96d96 Latest dependencies
• 2dd6989 Undo the assembly merge from #383
• 1c51d51 Latest dependencies
• Additional commits viewable in compare view

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[dependabot]

Looks like these dependencies are updatable in another way, so this is no longer needed.