Prefer %s format over %S for buffers

This restores the `%s` format` for buffers
after fba3c7ff3f.

* lisp/gnus/nnimap.el (nnimap-make-process-buffer):
* lisp/gnus/nntp.el (nntp-make-process-buffer):
* lisp/simple.el (next-error-internal):
Prefer more user-readable `%s` format over `%S` for buffers.

lisp/gnus/nnimap.el

@@ -386,7 +386,7 @@ during splitting, which may be slow."
 
 (defun nnimap-make-process-buffer (buffer)
   (with-current-buffer
-      (generate-new-buffer (format " *nnimap %s %s %S*"
+      (generate-new-buffer (format " *nnimap %s %s %s*"
 				   nnimap-address nnimap-server-port
                                    buffer))
     (mm-disable-multibyte)

lisp/gnus/nntp.el

@@ -1189,7 +1189,7 @@ If SEND-IF-FORCE, only send authinfo to the server if the
   "Create a new, fresh buffer usable for nntp process connections."
   (with-current-buffer
       (generate-new-buffer
-       (format " *server %s %s %S*"
+       (format " *server %s %s %s*"
                nntp-address nntp-port-number buffer))
     (gnus-add-buffer)
     (mm-disable-multibyte)

lisp/simple.el

@@ -393,7 +393,7 @@ To control which errors are matched, customize the variable
       (next-error-found buffer (current-buffer))
       (when (or next-error-verbose
                 (not (eq prev next-error-last-buffer)))
-        (message "Current locus from %S" next-error-last-buffer)))))
+        (message "Current locus from %s" next-error-last-buffer)))))
 
 (defun next-error-quit-window (from-buffer to-buffer)
   "Quit window of FROM-BUFFER when the prefix arg is 0.