Remove old 2009 syntax of Flexbox (i.e -webkit-box, -webkit-box-*) which is no longer supported

Author: cr101

packages/react-scripts/template/README.md

@@ -427,16 +427,12 @@ becomes this:
 
 ```css
 .App {
-  display: -webkit-box;
   display: -ms-flexbox;
   display: flex;
-  -webkit-box-orient: horizontal;
-  -webkit-box-direction: normal;
-      -ms-flex-direction: row;
-          flex-direction: row;
-  -webkit-box-align: center;
-      -ms-flex-align: center;
-          align-items: center;
+  -ms-flex-direction: row;
+  flex-direction: row;
+  -ms-flex-align: center;
+  align-items: center;  
 }
 ```