chore: Bump TUnit.Assertions from 1.12.125 to 1.21.6

---
updated-dependencies:
- dependency-name: TUnit.Assertions
  dependency-version: 1.21.6
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -6,6 +6,6 @@
     <PackageVersion Include="DotNet.ReproducibleBuilds" Version="2.0.2" />
     <PackageVersion Include="Microsoft.Playwright" Version="1.58.0" />
     <PackageVersion Include="TUnit" Version="1.12.125" />
-    <PackageVersion Include="TUnit.Assertions" Version="1.12.125" />
+    <PackageVersion Include="TUnit.Assertions" Version="1.21.6" />
   </ItemGroup>
 </Project>