Update global.json (#17669)

Author: wenhx

aspnetcore/mvc/controllers/testing/samples/3.x/TestingControllersSample/tests/global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": 3.0.100"
+    "version": "3.0.100"
   }
-}
+}