css-viewport-1: number / percentage should be alternates, not optionals

Author: keithamus

css-viewport-1/Overview.bs

@@ -419,7 +419,7 @@ Note: 'zoom' does not affect or prevent 'transform' scaling.
 
 <pre class="propdef">
 	Name: zoom
-	Value: <<number [0,∞]>> || <<percentage [0,∞]>>
+	Value: <<number [0,∞]>> | <<percentage [0,∞]>>
 	Initial: 1
 	Applies to: all <<length>> property values of all elements
 	Inherited: no