test-org-attach-git: Fix file name in header and footer

* testing/lisp/test-org-attach-git.el: Update file name in the header
and footer to match the actual file name.

testing/lisp/test-org-attach-git.el

@@ -1,4 +1,4 @@
-;;; test-org-annex-attach.el --- Tests for Org Attach with git-annex
+;;; test-org-attach-git.el --- Tests for Org Attach with git-annex
 ;;
 ;; Copyright (c) 2016, 2019 Erik Hetzner
 ;; Authors: Erik Hetzner
@@ -92,4 +92,4 @@
 	   (should (string-equal "hello world\n" (buffer-string))))
 	 (should (eq called 'was-called)))))))
 
-;;; test-org-attach-annex.el ends here
+;;; test-org-attach-git.el ends here