chore(core): remove depreciated slash command related_ticket

This was migrated to the new slash command and is feature-to-feature the same

ref: #1188 #273

Author: jon-nfc

app/core/lib/slash_commands/__init__.py

@@ -1,14 +1,12 @@
 import re
 
-from .linked_model import CommandLinkedModel    # depreciated model
 from .link_model import CommandLinkModelTicket
 from .ticket_dependency import CommandTicketDependency
 from .time_track import CommandTimeTrack
 
 
 
 class SlashCommands(
-    CommandLinkedModel,    # depreciated model
     CommandLinkModelTicket,
     CommandTicketDependency,
     CommandTimeTrack,