Bump Shouldly from 3.0.2 to 4.0.0 in /src

Bumps [Shouldly](https://github.com/shouldly/shouldly) from 3.0.2 to 4.0.0.
- [Release notes](https://github.com/shouldly/shouldly/releases)
- [Changelog](https://github.com/shouldly/shouldly/blob/master/BREAKING%20CHANGES.txt)
- [Commits](shouldly/shouldly@v3.0.2...v4.0.0)

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

src/Cake.Issues.PullRequests.GitHubActions.Tests/Cake.Issues.PullRequests.GitHubActions.Tests.csproj

@@ -18,7 +18,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.8.0" />
     <PackageReference Include="Cake.Core" Version="0.33.0" />
     <PackageReference Include="Cake.Testing" Version="0.33.0" />
-    <PackageReference Include="Shouldly" Version="3.0.2" />
+    <PackageReference Include="Shouldly" Version="4.0.0" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.1.118" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />