fix(CSS): too much overflow in the example output

Author: OnkarRuikar

learn/overflow/block-overflow.html

@@ -11,7 +11,7 @@
     <style class="editable">
       .box {
         border: 1px solid #333333;
-        width: 200px;
+        width: 350px;
         height: 100px;
       }
     </style>
@@ -25,7 +25,7 @@
     <textarea class="playable playable-css" style="height: 120px;">
 .box {
   border: 1px solid #333333;
-  width: 200px;
+  width: 350px;
   height: 100px;
 }
     </textarea>