Document `wp` defgroup as obsolete instead of deprecated

This opens up for its removal at some point in the future.  It has
been deprecated for the better part of a decade by now.

* lisp/cus-edit.el (wp): Document group "wp" as obsolete.
* lisp/finder.el (finder-known-keywords): Document keyword "wp" as obsolete.

lisp/cus-edit.el

@@ -177,7 +177,7 @@
 
 (defgroup wp nil
   "Support for editing text files.
-Use group `text' for this instead.  This group is deprecated."
+Use group `text' for this instead.  This group is obsolete."
   :group 'emacs)
 
 (defgroup text nil

lisp/finder.el

@@ -72,7 +72,7 @@
     (tools	. "programming tools")
     (unix	. "UNIX feature interfaces and emulators")
     (vc		. "version control")
-    (wp		. "use keyword `text' instead; this keyword is deprecated"))
+    (wp		. "use keyword `text' instead; this keyword is obsolete"))
   "Association list of the standard \"Keywords:\" headers.
 Each element has the form (KEYWORD . DESCRIPTION).")