Do we still need to support 3.x branch?

Problem/Motivation

Currently we support the 8.x-3.x and 4.x versions of Scheduled Publish.

3.x still supports D8.

Approximately half of current usage is on 3.x, while half is on 4.x. However, as 4.0.0 has minimal differences from 8.x-3.11, upgrading from 3.x to 4.x is fairly painless.

Steps to reproduce

N/A

Proposed resolution

Mark 8.x-3.x unsupported.

Remaining tasks

Wait for confirmation that 3.x can be deprecated.

User interface changes

N/A

API changes

N/A

Data model changes

N/A