Bump NuGet/setup-nuget from 2 to 3

Bumps [NuGet/setup-nuget](https://github.com/nuget/setup-nuget) from 2 to 3.
- [Release notes](https://github.com/nuget/setup-nuget/releases)
- [Commits](NuGet/setup-nuget@v2...v3)

---
updated-dependencies:
- dependency-name: NuGet/setup-nuget
  dependency-version: '3'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/runtests.yml

@@ -22,7 +22,7 @@ jobs:
         with:
           fetch-depth: 0  # needed for GitVersioning to work
       - name: Setup NuGet
-        uses: NuGet/setup-nuget@v2
+        uses: NuGet/setup-nuget@v3
       - name: Cache NuGet packages
         uses: actions/cache@v5
         id: cache
@@ -61,7 +61,7 @@ jobs:
         with:
           fetch-depth: 0
       - name: Setup NuGet
-        uses: NuGet/setup-nuget@v2
+        uses: NuGet/setup-nuget@v3
       - name: Cache NuGet packages
         uses: actions/cache@v5
         id: cache