[indexes] Fix Bikeshed errors.

Author: tabatkins

indexes/Overview.bs

@@ -37,24 +37,24 @@ or draw from all specs.)
 Properties and Descriptors {#properties}
 ========================
 
-<index type="property, descriptor" for=*></index>
+<index type="property, descriptor"></index>
 
 Property/Descriptor Values {#values}
 ====================================
 
-<index type=value for=*></index>
+<index type=value></index>
 
 Functions {#functions}
 ======================
 
-<index type=function for=*></index>
+<index type=function></index>
 
 At-Rules {#at-rules}
 ====================
 
-<index type=at-rule for=*></index>
+<index type=at-rule></index>
 
 Selectors {#selectors}
 ======================
 
-<index type=selector for=*></index>
+<index type=selector></index>