Refactor: (DWS) Remove deprecated and unused slash_command prompt expansion code
Problem to solve
There is currently unused code that needs to be cleaned up within the Duo Workflow service codebase from when we were implementing the slash commands in agentic chat.
Proposal
Remove unused classes in the slash_command directory and create a follow-up issue for moving the
Further details
This will help keep our codebase clean and prevent confusion when trying to troubleshoot any bugs that may arise in the future with slash commands and prompt expansions