Create new slack token and delete disabled one

Accidentally leaked slack token via an unused variable in `projects-activity.php`, need to remove that and get a new one configured on the instance

Start by reviewing projects-activity.php to locate the unused Slack token reference and confirm how the instance receives its configuration. The work is done when the leaked token reference is removed, the disabled token is replaced on the instance, and Slack activity still works; no test file is mentioned.

Written by the indexing model from the issue text.