bta_av_aact: Remove unused code

p_data->ci_setconfig.num_seid is always 0 according to
invocations of bta_av_ci_setconfig.
Bug: 329809288
Flag: EXEMPT - minor refactor
Test: mmm packages/modules/Bluetooth

Change-Id: If99d6c701288a191461c8be0d1444f048be59185