[css-round-display] change the initial value of offset-rotation to 0deg

Author: Jihye Hong

css-round-display/Overview.bs

@@ -747,7 +747,7 @@ With the former, the position of the element changes when the value of the margi
 <pre class='propdef'>
     Name: offset-rotation
     Value: [ auto | reverse ] || <<angle>>
-    Initial: auto
+    Initial: 0
     Applies to: All elements. In SVG, it applies to <a href="">container elements</a> excluding the <{defs}> element and all <a>graphics elements</a>
     Inherited: no
     Percentages: n/a