Merge pull request #1260 from dotnet/dependabot/nuget/Rx.NET/Source/MSBuild.Sdk.Extras-2.1.2

Rx.NET/Source/global.json

@@ -1,5 +1,5 @@
 {
   "msbuild-sdks": {
-    "MSBuild.Sdk.Extras": "2.0.54"
+    "MSBuild.Sdk.Extras": "2.1.2"
   }
 }