Bump TUnit from 1.19.74 to 1.21.20 (#217)

---
updated-dependencies:
- dependency-name: TUnit
  dependency-version: 1.21.20
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -44,7 +44,7 @@
     <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.12" />
     <PackageVersion Include="System.CommandLine" Version="2.0.5" />
     <PackageVersion Include="System.Drawing.Common" Version="10.0.4" />
-    <PackageVersion Include="TUnit" Version="1.19.74" />
+    <PackageVersion Include="TUnit" Version="1.21.20" />
     <PackageVersion Include="Velopack" Version="0.0.1298" />
     <PackageVersion Include="Microsoft.Web.WebView2" Version="1.0.3856.49" />
   </ItemGroup>