Make turn-on-flyspell/turn-off-flyspell obsolete

* lisp/textmodes/flyspell.el (turn-on-flyspell): Make into obsolete
function alias for 'flyspell-mode'.
(turn-off-flyspell): Declare obsolete.
(text-mode-hook): Don't redundantly set :options here.
* lisp/textmodes/text-mode.el (text-mode-hook): Prefer 'flyspell-mode'
to 'turn-on-flyspell' in :options.  (Bug#76535)

etc/NEWS

@@ -1065,6 +1065,12 @@ allows idle timers and other code to run during this delay period.  We
 consider making this behavior the default in a future Emacs version, so
 we invite Flyspell users to enable this new option and report issues.
 
+---
+*** 'turn-on-flyspell' and 'turn-off-flyspell' are obsolete.
+To unconditionally enable 'flyspell-mode' from a hook, use this instead:
+
+    (add-hook 'text-mode-hook #'flyspell-mode)
+
 ** Tramp
 
 +++

lisp/textmodes/flyspell.el

@@ -530,18 +530,6 @@ in your init file.
 	       (flyspell-mode -1)))
     (flyspell--mode-off)))
 
-;;;###autoload
-(defun turn-on-flyspell ()
-  "Unconditionally turn on Flyspell mode."
-  (flyspell-mode 1))
-
-;;;###autoload
-(defun turn-off-flyspell ()
-  "Unconditionally turn off Flyspell mode."
-  (flyspell-mode -1))
-
-(custom-add-option 'text-mode-hook 'turn-on-flyspell)
-
 (defvar flyspell-buffers nil
   "For remembering buffers running flyspell.")
 (make-obsolete-variable 'flyspell-buffers "not used." "28.1")
@@ -2408,6 +2396,15 @@ This function is meant to be added to `flyspell-incorrect-hook'."
 (define-obsolete-function-alias 'flyspell-mode-on 'flyspell--mode-on "30.1")
 (define-obsolete-function-alias 'flyspell-mode-off 'flyspell--mode-off "30.1")
 
+;;;###autoload
+(define-obsolete-function-alias 'turn-on-flyspell #'flyspell-mode "31.1")
+
+;;;###autoload
+(defun turn-off-flyspell ()
+  "Unconditionally turn off Flyspell mode."
+  (declare (obsolete flyspell-mode "31.1"))
+  (flyspell-mode -1))
+
 (provide 'flyspell)
 
 ;;; flyspell.el ends here

lisp/textmodes/text-mode.el

@@ -34,7 +34,8 @@
 (defcustom text-mode-hook '(text-mode-hook-identify)
   "Normal hook run when entering Text mode and many related modes."
   :type 'hook
-  :options '(turn-on-auto-fill turn-on-flyspell)
+  :options '(turn-on-auto-fill flyspell-mode)
+  :version "31.1"
   :group 'text)
 
 (defvar text-mode-variant nil