bpf: Add Jiayuan Chen to sockmap maintainers

bpf: Add Jiayuan Chen to sockmap maintainers

Nominate Jiayuan Chen for the sockmap co-maintainer. Jiayuan has been a
regular contributor and reviewer for the sockmap and networking code.

Since we are now down to just two maintainers, and John has to split his
time between BPF core, BPF networking, and sockmap, having three
maintainers again will help with the review load.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260511-sockmap-ktls-fix-1-v1-1-96ff8c1906e4@cloudflare.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>