Revert previous update of the .net sdk as the AppVeyor Ubuntu image is not ready for it (and the commit was not supposed to go to development directly)

Author: bergmeister

global.json

@@ -1,5 +1,5 @@
 {
     "sdk": {
-        "version": "2.1.403"
+        "version": "2.1.101"
     }
 }