powerpc/configs/64s: Drop IPV6 which is default y

Since commit de551f2e ("net: Build IPv6 into kernel by default"),
IPV6 is default y.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230414132415.821564-3-mpe@ellerman.id.au

arch/powerpc/configs/ppc64_defconfig

@@ -84,7 +84,6 @@ CONFIG_SYN_COOKIES=y
 CONFIG_INET_AH=m
 CONFIG_INET_ESP=m
 CONFIG_INET_IPCOMP=m
-CONFIG_IPV6=y
 CONFIG_NETFILTER=y
 # CONFIG_NETFILTER_ADVANCED is not set
 CONFIG_BRIDGE=m