Bump actions/download-artifact from 2 to 4.1.7 in /.github/workflows

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 2 to 4.1.7.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v2...v4.1.7)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
...

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

.github/workflows/dotnetcore.yml

@@ -120,19 +120,19 @@ jobs:
         dotnet-version: 6.0.x
 
     - name: Download macOS Lib
-      uses: actions/download-artifact@v2
+      uses: actions/download-artifact@v4.1.7
       with:
         name: libspreads_native.dylib
         path: dotnet/lib/runtimes/osx-x64/native
 
     - name: Download Linux Lib
-      uses: actions/download-artifact@v2
+      uses: actions/download-artifact@v4.1.7
       with:
         name: libspreads_native.so
         path: dotnet/lib/runtimes/linux-x64/native
 
     - name: Download Windows Lib
-      uses: actions/download-artifact@v2
+      uses: actions/download-artifact@v4.1.7
       with:
         name: spreads_native.dll
         path: dotnet/lib/runtimes/win-x64/native