[cssom] [css-page] Fix orientation in CSSPageDescriptors to be page-orientation and pageOrientation.

Author: AlaskanEmily

cssom-1/Overview.bs

@@ -2131,7 +2131,8 @@ interface CSSPageDescriptors : CSSStyleDeclaration {
   attribute [LegacyNullToEmptyString] CSSOMString margin-bottom;
   attribute [LegacyNullToEmptyString] CSSOMString margin-left;
   attribute [LegacyNullToEmptyString] CSSOMString size;
-  attribute [LegacyNullToEmptyString] CSSOMString orientation;
+  attribute [LegacyNullToEmptyString] CSSOMString pageOrientation;
+  attribute [LegacyNullToEmptyString] CSSOMString page-orientation;
   attribute [LegacyNullToEmptyString] CSSOMString marks;
   attribute [LegacyNullToEmptyString] CSSOMString bleed;
 };