Make two old function aliases obsolete

* lisp/textmodes/bibtex.el (bibtex-find-crossref)
(bibtex-find-entry): Make function aliases obsolete.  These were left
behind when renaming functions, but never declared obsolete.

lisp/gnus/gnus-registry.el

@@ -1142,7 +1142,7 @@ non-nil."
            entry)
       (while (car-safe old)
         (cl-incf count)
-        ;; don't use progress reporters for backwards compatibility
+        ;; todo: use progress reporters.
         (when (and (< 0 expected)
                    (= 0 (mod count 100)))
           (message "importing: %d of %d (%.2f%%)"

lisp/textmodes/bibtex.el

@@ -4317,8 +4317,6 @@ for a crossref key, t otherwise."
           (eqb (goto-char pos))
           (t (set-buffer buffer) (goto-char pos)))
     pos))
-;; backward compatibility
-(defalias 'bibtex-find-crossref 'bibtex-search-crossref)
 
 (defun bibtex-dist (pos beg end)
   "Return distance between POS and region delimited by BEG and END."
@@ -4381,8 +4379,6 @@ A prefix arg negates the value of `bibtex-search-entry-globally'."
              (if display (bibtex-reposition-window)))
             (display (message "Key `%s' not found" key)))
       pnt)))
-;; backward compatibility
-(defalias 'bibtex-find-entry 'bibtex-search-entry)
 
 (defun bibtex-prepare-new-entry (index)
   "Prepare a new BibTeX entry with index INDEX.
@@ -5608,5 +5604,8 @@ If APPEND is non-nil, append ENTRIES to those already displayed."
   (setq buffer-read-only t)
   (goto-char (point-min)))
 
+(define-obsolete-function-alias 'bibtex-find-crossref #'bibtex-search-crossref "29.1")
+(define-obsolete-function-alias 'bibtex-find-entry #'bibtex-search-entry "29.1")
+
 (provide 'bibtex)
 ;;; bibtex.el ends here