Issue Summary

In Help Center, requester of a ticket is unable to remove participants, however they are allowed to add the participants on the same ticket. This happens because of minor discrepancies in the permission checks while reading that user has permission to remove participant and while actually removing the participant.

https://getsupport.atlassian.com/browse/PCS-114701

Steps to Reproduce

1. Add a user as a customer to a JSM project
2. Update customer sharing permission to the following
   
3. Create an organisation and add this customer to that org along with some other users
4. Now when the customer(requester of ticket) would try to add other users of their org as participants they would be allowed to do so, however, removing the participant would not be allowed to them.

Expected Results

The customer(who created the ticket and added some participants) should be able to remove the participants from the ticket.

Actual Results

The customer should be able to remove relevant participants from the ticket.

Workaround

Customer can request some admins/agents of the site to remove the participants from the ticket. Other than this it might not be possible for the customer to remove participant.