Users/thboop/port3.0changes (#143)

* consume dotnet core 3.0

* update linux dependency doc.

src/Runner.Sdk/ActionPlugin.cs

@@ -70,13 +70,6 @@ namespace GitHub.Runner.Sdk
 
             VssClientHttpRequestSettings.Default.UserAgent = headerValues;
 
-#if OS_LINUX || OS_OSX
-            // The .NET Core 2.1 runtime switched its HTTP default from HTTP 1.1 to HTTP 2.
-            // This causes problems with some versions of the Curl handler.
-            // See GitHub issue https://github.com/dotnet/corefx/issues/32376
-            VssClientHttpRequestSettings.Default.UseHttp11 = true;
-#endif
-
             var certSetting = GetCertConfiguration();
             if (certSetting != null)
             {