Hello. When trunks are created the spanning-tree priority for them is lowered so that they are preferred over single links of the same speed (and path-cost) downstream. There is no effect when spanning-tree is disabled.
8 is the default priority. If you don't plan on enabling spanning-tree and really do not want to see it displayed in "show run" you could set the priority manually. If it were me I'd leave it alone.
HP-Stack-2920(config)# show run interface trk1
Running configuration:
interface Trk1
untagged vlan 1
spanning-tree priority 4
exit
HP-Stack-2920(config)# span trk1 priority 8
HP-Stack-2920(config)# show run interface trk1
Running configuration:
interface Trk1
untagged vlan 1
exit