docs/configuring-playbook-bridge-appservice-slack.md is outdated in that creation of classic Slack app was discontinued

[luixxiul]

Describe the bug

docs/configuring-playbook-bridge-appservice-slack.md mentions a classic Slack app here and here, but it seems no longer possible to create a new classic app since the last June. See: matrix-org/matrix-appservice-slack#789

matrix-org/matrix-appservice-slack#789 (comment) says:

Currently the best (and only) option for new installations is to use the webhook bridging.

Because matrix-appservice-webhooks is no longer maintained as we claim here, it seems matrix-hookshot should be suggested for new installations.

To Reproduce

Expected behavior

• Add the note to docs/configuring-playbook-bridge-appservice-slack.md that it has been unavailable to use for new installations since the last June.
• Add the link to the documentation to docs/configuring-playbook-bridge-hookshot.md, claiming that the webhook is the only effective solution for new installations for now.

Matrix Server:

Ansible:

Client:

Additional context

I am wondering if the discontinuation of a new classic app would possibly affect the other two bridges for Slack, Mautrix Slack bridging and MX Puppet Slack bridging as well.