; Improve obsolescence of 'text-mode-variant'

* lisp/textmodes/text-mode.el (text-mode-variant): Improve
obsolescence announcement text.

* doc/lispref/modes.texi (Example Major Modes): Update example.
(Bug#78125).

doc/lispref/modes.texi

@@ -1509,9 +1509,6 @@ You can thus get the full benefit of adaptive filling
  (see the variable `adaptive-fill-mode').
 \\@{text-mode-map@}
 Turning on Text mode runs the normal hook `text-mode-hook'."
-@end group
-@group
-  (setq-local text-mode-variant t)
   (setq-local require-final-newline mode-require-final-newline))
 @end group
 @end smallexample

lisp/textmodes/text-mode.el

@@ -39,7 +39,9 @@
 
 (defvar text-mode-variant nil
   "Non-nil if this buffer's major mode is a variant of Text mode.")
-(make-obsolete-variable 'text-mode-variant 'derived-mode-p "27.1")
+(make-obsolete-variable 'text-mode-variant
+                        "\
+Don't set it, and instead of testing its value use `derived-mode-p'." "27.1")
 
 ;; Actually defined in textconv.c.
 (defvar text-conversion-style)