lisp/ox.el (org-export-to-file): Don't load the major mode

* lisp/ox.el (org-export-to-file): Don't load the major mode.

Prior to this, when `org-export-to-file' was called it activated the
major mode for that file type based on `auto-mode-alist'.  This can be
mildly annoying in various ways as loading the major mode (1) makes
the export take longer, (2) can produce unwanted "noise" while
initialising, namely warnings and errors related to the mode itself,
(3) can produce spurious files like an .auctex-auto folder.  By
locally binding `auto-mode-alist' to nil, all of these undesirable
behaviours can be avoided.

Link: https://orgmode.org/list/87lfa3fips.fsf@gmail.com/

lisp/ox.el

@@ -6394,7 +6394,8 @@ or FILE."
   (declare (indent 2))
   (if (not (file-writable-p file)) (error "Output file not writable")
     (let ((ext-plist (org-combine-plists `(:output-file ,file) ext-plist))
-	  (encoding (or org-export-coding-system buffer-file-coding-system)))
+	  (encoding (or org-export-coding-system buffer-file-coding-system))
+          auto-mode-alist)
       (if async
           (org-export-async-start
 	      (lambda (file)