LLD-based Triggers are not changed if its items are in "Not discovered anymore" state

To reproduce:
1. Add new test trigger to default OS LINUX Template under Network Interfaces discovery. (Template should be attached to a host like Zabbix Server)
with expression:

	{Template OS Linux:net.if.in[{#IFNAME}].last()}>0

2. Change Network Interfaces discovery update interval to 30-60 seconds
for OS LINUX Template.

3. Wait for the triggers to appear for each network interface available on Zabbix Server

4. Now change discovery filter regex:

5. Wait for interface items to become "Not discovered anymore"

6. Change trigger prototype name and expression to something else

7. Go to Zabbix Server triggers: only triggers for others interfaces(that are still discoverable were updated)