[github-actions] Update .NET Core version to 5.0.x in GitHub Actions workflow (#714)

Author: Dor-bl

.github/workflows/release-nuget.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 3.1.x
+        dotnet-version: 5.0.x
 
     - name: Install dependencies
       run: dotnet restore src/Appium.Net.sln