Revert "Add CategoryAPICategory to the complete API index"

This reverts commit 21a42d2b0d7441004b6dc463fd8e936696c64f2b.

It doesn't work like this, sorry.  :)

build-scripts/wikiheaders.pl

@@ -2627,12 +2627,6 @@ if ($copy_direction == 1) {  # --copy-to-headers
 
 <!-- END CATEGORY DOCUMENTATION -->
 
-## Categories
-
-<!-- DO NOT HAND-EDIT CATEGORY LISTS, THEY ARE AUTOGENERATED AND WILL BE OVERWRITTEN, BASED ON TAGS IN INDIVIDUAL PAGE FOOTERS. EDIT THOSE INSTEAD. -->
-<!-- BEGIN CATEGORY LIST: Category$cat, CategoryAPICategory -->
-<!-- END CATEGORY LIST -->
-
 ## Functions
 
 <!-- DO NOT HAND-EDIT CATEGORY LISTS, THEY ARE AUTOGENERATED AND WILL BE OVERWRITTEN, BASED ON TAGS IN INDIVIDUAL PAGE FOOTERS. EDIT THOSE INSTEAD. -->