Fix non-ASCII filename operatiion on EasyPG (bug#71500)

* lisp/epg.el (epg--start): Don't encode command-line arguments for
gpg2 program in raw-text.

lisp/epg.el

@@ -676,10 +676,11 @@ callback data (if any)."
 				    :command (cons (epg-context-program context)
 						   args)
 				    :connection-type 'pipe
-				    :coding 'raw-text
+				    :coding '(raw-text . nil)
 				    :filter #'epg--process-filter
 				    :stderr error-process
 				    :noquery t))))
+    (set-process-coding-system process 'raw-text 'raw-text)
     (setf (epg-context-process context) process)))
 
 (defun epg--process-filter (process input)