Use 'buffer-file-name' when matching 'auto-mode-alist'

* lisp/emacs-lisp/package-activate.el (package--suggestion-applies-p):
The file name associated with a buffer is a better match for
entries in 'auto-mode-alist', so we use that instead of the
buffer name that can have additional noise to make the name unique.

lisp/emacs-lisp/package-activate.el

@@ -588,7 +588,7 @@ what command to invoke to enable the package."
          `(,(pred package-installed-p) . ,_))
      nil)
     (`(,_ auto-mode-alist ,ext . ,_)
-     (and (string-match-p ext (buffer-name)) t))
+     (and (buffer-file-name) (string-match-p ext (buffer-file-name)) t))
     (`(,_ magic-mode-alist ,mag . ,_)
      (without-restriction
        (save-excursion