Merge pull request #962 from dotnet/dependabot/nuget/Rx.NET/Source/MSBuild.Sdk.Extras-2.0.31

Bump MSBuild.Sdk.Extras from 2.0.29 to 2.0.31 in /Rx.NET/Source

Author: Oren Novotny

Rx.NET/Source/global.json

@@ -3,6 +3,6 @@
     "version": "3.0.100-preview"
   },
   "msbuild-sdks": {
-    "MSBuild.Sdk.Extras": "2.0.29"
+    "MSBuild.Sdk.Extras": "2.0.31"
   }
 }