Remove old fish_pager source and implementation

complete.h

@@ -55,13 +55,6 @@
  */
 #define COMPLETE_SEP_STR L"\004"
 
-/**
- * Separator between completion items in fish_pager. This is used for
- * completion grouping, e.g. when putting completions with the same
- * descriptions on the same line.
- */
-#define COMPLETE_ITEM_SEP L'\uf500'
-
 /**
  * Character that separates the completion and description on
  * programmable completions