Hi!
The Trk2 you created (like all the others I see) is curiously made of one physical interface only (nornally a Port Trunk in ArubaOS-Switch jargon = Links Aggregation -> will require two or more physical ports to be aggregated together to form a Trk<x> logical interface with or without LACP)...you can't remove it and pretend to leave the logical interface Trk2 to exist without any member.
You need to entirely destroy (delete) the logical interface Trk2 definition by removing its only member port and so, at that point, the lonely physical interface 4 will be freed and be reset to its default values/status (even including its VLAN Membership which, when it was part of Trk2, was managed at Trk2 level only).
Try with:
SWCORE-DAV-EDFAP-1-RESPALDO# show trunks
SWCORE-DAV-EDFAP-1-RESPALDO# show running-config interface ethernet 4
SWCORE-DAV-EDFAP-1-RESPALDO# config
SWCORE-DAV-EDFAP-1-RESPALDO(config)# no trunk ethernet 4
SWCORE-DAV-EDFAP-1-RESPALDO(config)# write memory
SWCORE-DAV-EDFAP-1-RESPALDO(config)# exit
SWCORE-DAV-EDFAP-1-RESPALDO# show trunks
SWCORE-DAV-EDFAP-1-RESPALDO# show running-config interface ethernet 4