uapi: in6: replace temporary label with rfc9486

Not really a fix per se, but IPV6_TLV_IOAM is still tagged as "TEMPORARY
IANA allocation for IOAM", while RFC 9486 is available for some time
now. Just update the reference.

Fixes: 9ee11f0f ("ipv6: ioam: Data plane support for Pre-allocated Trace")
Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240226124921.9097-1-justin.iurman@uliege.beSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/uapi/linux/in6.h

@@ -145,7 +145,7 @@ struct in6_flowlabel_req {
 #define IPV6_TLV_PADN		1
 #define IPV6_TLV_ROUTERALERT	5
 #define IPV6_TLV_CALIPSO	7	/* RFC 5570 */
-#define IPV6_TLV_IOAM		49	/* TEMPORARY IANA allocation for IOAM */
+#define IPV6_TLV_IOAM		49	/* RFC 9486 */
 #define IPV6_TLV_JUMBO		194
 #define IPV6_TLV_HAO		201	/* home address option */