Config.in.legacy: drop 2021.08 entry duplicate

Drop 2021.08 entry duplicate added with commit
531b2a10cda6bae78ecc141c9fe48f2024f71dbc

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Config.in.legacy

@@ -224,8 +224,6 @@ config BR2_PACKAGE_PHP_EXT_XMLRPC
 	  The XMLRPC php extension was removed.
 	  See: https://wiki.php.net/rfc/unbundle_xmlprc
 
-comment "Legacy options removed in 2021.08"
-
 config BR2_GCC_VERSION_8_X
 	bool "gcc 8.x support removed"
 	select BR2_LEGACY