Don't obsolete the _command_ replace-buffer-contents

* lisp/subr.el (replace-buffer-contents): Don't obsolete
function.  Its purpose is to serve as a command and such
obsoletion was unnecessary to begin with.

etc/NEWS

@@ -1757,7 +1757,6 @@ Previously, its argument was always evaluated using dynamic binding.
 It has been promoted from 'subr-x' to the C code.
 You can now directly pass it a string or a buffer rather than a function.
 Actually passing it a function is now deprecated.
-'replace-buffer-contents' is also marked as obsolete.
 
 +++
 ** New macros 'static-when' and 'static-unless'.

lisp/subr.el

@@ -4770,7 +4770,6 @@ Interactively, prompt for SOURCE.
 The replacement is performed using `replace-region-contents'
 which also describes the MAX-SECS and MAX-COSTS arguments and the
 return value."
-  (declare (obsolete replace-region-contents "31.1"))
   (interactive "bSource buffer: ")
   (replace-region-contents (point-min) (point-max) (get-buffer source)
                            max-secs max-costs))