language strings should not be generated programmatically

Some of the strings in auth/openid/lang/en_utf8/auth_openid.php are dynamically generated (e.g. openid_note_user, confirm_append, confirm_change). Dynamically generated strings may break things, such as the language strings editor. Notably, one cannot use the Moodle language strings editor to edit the openid_note_user string without producing a broken logout link. Instead, the logout link should be passed in as the $a parameter.