Revert commits dafa6d6b and 72c45fa9

These were there to work around deficiencies in how Eshell produces
completions for 'pcomplete-argument' (Eshell passed various non-string
objects to Pcomplete, which broke things).  Now, Eshell always returns
a stringified form of the argument, with the original value stored via
the text property 'pcomplete-arg-value'.

* lisp/pcomplete.el (pcomplete-arg): Revert changes back to a simpler
form.

lisp/pcomplete.el

@@ -685,35 +685,13 @@ parts of the list.
 
 The OFFSET argument is added to/taken away from the index that will be
 used.  This is really only useful with `first' and `last', for
-accessing absolute argument positions.
-
-When the argument has been transformed into something that is not
-a string by `pcomplete-parse-arguments-function', the text
-representation of the argument, namely what the user actually
-typed in, is returned, and the value of the argument is stored in
-the pcomplete-arg-value text property of that string."
-  (let ((arg
-         (nth (+ (pcase index
-	           ('first 0)
-	           ('last  pcomplete-last)
-	           (_      (- pcomplete-index (or index 0))))
-	         (or offset 0))
-              pcomplete-args)))
-    (if (or (stringp arg)
-            ;; FIXME: 'last' is handled specially in Emacs 29, because
-            ;; 'pcomplete-parse-arguments' accepts a list of strings
-            ;; (which are completion candidates) as return value for
-            ;; (pcomplete-arg 'last).  See below: "it means it's a
-            ;; list of completions computed during parsing,
-            ;; e.g. Eshell uses that to turn globs into lists of
-            ;; completions".  This special case will be dealt with
-            ;; differently in Emacs 30: the pcomplete-arg-value
-            ;; property will be used by 'pcomplete-parse-arguments'.
-            (eq index 'last))
-        arg
-      (propertize
-       (car (split-string (pcomplete-actual-arg index offset)))
-       'pcomplete-arg-value arg))))
+accessing absolute argument positions."
+  (nth (+ (pcase index
+            ('first 0)
+            ('last  pcomplete-last)
+            (_      (- pcomplete-index (or index 0))))
+          (or offset 0))
+       pcomplete-args))
 
 (defun pcomplete-begin (&optional index offset)
   "Return the beginning position of the INDEXth argument.