Revert recent project-find-file change

* lisp/progmodes/project.el (project-find-file): Delete recently added
'filename' arg; just use project-find-file-in.

lisp/progmodes/project.el

@@ -443,14 +443,14 @@ pattern to search for."
     (read-regexp "Find regexp" (and id (regexp-quote id)))))
 
 ;;;###autoload
-(defun project-find-file (&optional filename)
+(defun project-find-file ()
   "Visit a file (with completion) in the current project's roots.
 The completion default is the filename at point, if one is
 recognized."
   (interactive)
   (let* ((pr (project-current t))
          (dirs (project-roots pr)))
-    (project-find-file-in (or filename (thing-at-point 'filename)) dirs pr)))
+    (project-find-file-in (thing-at-point 'filename) dirs pr)))
 
 ;;;###autoload
 (defun project-or-external-find-file ()