Bump NUnit3TestAdapter from 3.17.0 to 4.0.0 (#542)

Bumps [NUnit3TestAdapter](https://github.com/nunit/nunit3-vs-adapter) from 3.17.0 to 4.0.0.
- [Release notes](https://github.com/nunit/nunit3-vs-adapter/releases)
- [Commits](nunit/nunit3-vs-adapter@V3.17...V4.0.0)

---
updated-dependencies:
- dependency-name: NUnit3TestAdapter
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

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

src/ApprovalTests.Tests/ApprovalTests.Tests.csproj

@@ -9,7 +9,7 @@
     <PackageReference Include="ModuleInit.Fody" Version="2.1.1" PrivateAssets="All" />
     <PackageReference Include="itext7" Version="7.1.15" />
     <PackageReference Include="NUnit" Version="3.13.2" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.17.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.10.0" />
     <PackageReference Include="System.Management" Version="5.0.0" />
     <ProjectReference Include="..\ApprovalTests\ApprovalTests.csproj" />