Auto-generated Slack URL no longer works

[ajyong]

Repro Steps

1. Grab a valid Member ID from desktop Slack (mobile apps no longer expose member IDs)
2. Paste it into an upcoming Presenter's profile's Slack members id:
   
3. Click View Site from the Django admin

Expected

Slack loads in browser and/or launches the desktop app and handles the member ID.

Actual

When I click the Slack icon, it takes me to Slack's website where it tells me "The workspace has been deleted":

The link created looks like: https://edmontonpy.slack.com/team/UDG7Q7XQE (that's my Slack ID)
Which unravels to: https://lxggh5xb2f-edmontonpy.slack.com/?redir=%2Fteam%2FUDG7Q7XQE

Root Cause

It's likely if we change the link to point to devedmonton.slack.com, it will "just work". I'll assign to me to fix Someday™