Follow-up from "Resolve "Deactivate a user (with self-service reactivation)""

The following discussion from !17037 (merged) should be addressed:

@ashmckenzie started a discussion:
Just looking at the policies when a user is blocked and noticed the differences between blocked and deactivated are:
```
prevent :log_in
prevent :use_slash_commands
```
Not having prevent :log_in makes sense, but should we also have prevent :use_slash_commands ?

Edited Oct 16, 2019 by Manoj M J