Description:

pruning based on @svennd "at user" is removing all messages contrary to what the description says:
"Only prune content from these users (leave empty to prune everyone's content)"

Steps to reproduce:

1. (web interface) -> public channel 3 dots -> prune messages
2. @user_to_delete
3. (optional set time)
4. Prune

Expected behavior:

Remove messages for @user_to_delete

Actual behavior:

remove all messages prior to set time (if this option)

Server Setup Information:

• Version of Rocket.Chat Server: 0.68.0
• Operating System: 4.15.17-2-pve
• Deployment Method: tar
• Number of Running Instances: 1
• DB Replicaset Oplog: disabled
• NodeJS Version: v8.9.3