Bump NuGet/setup-nuget from 2 to 4

Bumps [NuGet/setup-nuget](https://github.com/nuget/setup-nuget) from 2 to 4.
- [Release notes](https://github.com/nuget/setup-nuget/releases)
- [Commits](NuGet/setup-nuget@v2...v4)

---
updated-dependencies:
- dependency-name: NuGet/setup-nuget
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/api-doctor.yml

@@ -34,7 +34,7 @@ jobs:
           6.x
           8.x
     - name: Install NuGet
-      uses: NuGet/setup-nuget@v2
+      uses: NuGet/setup-nuget@v4
     - name: Install ApiDoctor from NuGet
       run: nuget install ApiDoctor -Version $Env:APIDOCTOR_VERSION -OutputDirectory ./nuget -NonInteractive -DisableParallelProcessing
     - name: Validate v1.0 docs