selftests: net: sort .gitignore file

This is the result of `sort tools/testing/selftests/net/.gitignore`, but
preserving the comment at the top.
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Link: https://lore.kernel.org/r/20220829184748.1535580-1-axelrasmussen@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
+cmsg_sender
+fin_ack_lat
+gro
+hwtstamp_config
+ioam6_parser
+ip_defrag
 ipsec
+ipv6_flowlabel
+ipv6_flowlabel_mgr
 msg_zerocopy
-socket
+nettest
 psock_fanout
 psock_snd
 psock_tpacket
-stress_reuseport_listen
+reuseaddr_conflict
+reuseaddr_ports_exhausted
 reuseport_addr_any
 reuseport_bpf
 reuseport_bpf_cpu
 reuseport_bpf_numa
 reuseport_dualstack
-reuseaddr_conflict
-tcp_mmap
-udpgso
-udpgso_bench_rx
-udpgso_bench_tx
-tcp_inq
-tls
-txring_overwrite
-ip_defrag
-ipv6_flowlabel
-ipv6_flowlabel_mgr
-so_txtime
-tcp_fastopen_backup_key
-nettest
-fin_ack_lat
-reuseaddr_ports_exhausted
-hwtstamp_config
 rxtimestamp
-timestamping
-txtimestamp
+socket
 so_netns_cookie
+so_txtime
+stress_reuseport_listen
+tap
+tcp_fastopen_backup_key
+tcp_inq
+tcp_mmap
 test_unix_oob
-gro
-ioam6_parser
+timestamping
+tls
 toeplitz
 tun
-cmsg_sender
+txring_overwrite
+txtimestamp
+udpgso
+udpgso_bench_rx
+udpgso_bench_tx
 unix_connect
-tap
\ No newline at end of file