boards: mps2_an385: Re-enable networking tests

This reverts commit 6a361266
"boards: mps2_an385: Exclude platform from networking tests"

This would have found the issue described in #67762 where a
network test was failing because of wrong section placement.
All the simulated environments (qemu_x86 and native_sim) used
in network testing missed this problem, but could have easily
found if network tests would have been run in mps2_an385.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>