4.0: Deprecate `accept [:*]` and remove from docs

As we all discussed on Alembic Slack:

> the fact that people mark fields as public to be writeable and then can accidentally expose fields defeats the entire purpose of the change to private by default

> security can sometimes be annoying but having an allowlist is always always safer than having a denylist

> Like how when you delete a repo on GitHub it makes you type out the repo name.

Search the repository for `accept [:*]` and the documentation references named in the issue. Read the surrounding DSL implementation and related tests to determine how deprecation is represented and what replacement behavior is expected; the work is done when the syntax is deprecated and its documentation references are removed.

Written by the indexing model from the issue text.