Mark files.upload / rtm.connect as deprecated

[seratch]

See the following announcements:

• https://api.slack.com/changelog/2024-04-a-better-way-to-upload-files-is-here-to-stay
• https://api.slack.com/changelog/2024-04-discontinuing-new-creation-of-classic-slack-apps-and-custom-bots

Category (place an x in each of the [ ])

• [ ] bolt (Bolt for Java)
• [ ] bolt-{sub modules} (Bolt for Java - optional modules)
• [x] slack-api-client (Slack API Clients)
• [ ] slack-api-model (Slack API Data Models)
• [ ] *slack-api--kotlin-extension** (Kotlin Extensions for Slack API Clients)
• [ ] slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[seratch]

It seems that Codecov has some issues with their token resolution. I've re-generated the repo token and set it to this repo but it didn't help. Will check this out again tomorrow