Bump Shouldly from 3.0.2 to 4.3.0

---
updated-dependencies:
- dependency-name: Shouldly
  dependency-version: 4.3.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

Google.Authenticator.Tests/Google.Authenticator.Tests.csproj

@@ -12,7 +12,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
-    <PackageReference Include="Shouldly" Version="3.0.2" />
+    <PackageReference Include="Shouldly" Version="4.3.0" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
       <PrivateAssets>all</PrivateAssets>