Update pip install instructions

[matthewshaver]

Contributions

• I have read the contribution docs, and understand what's expected of me.

Link to the page on docs.getdbt.com requiring updates

https://docs.getdbt.com/docs/core/pip-install

What part(s) of the page would you like to see updated?

dbt is back!

Update this blurb to mention the timeline:

Since v0.13, PyPI package named dbt was a simple "pass-through" of dbt-core and the four original database adapter plugins
Upon the release of dbt-core v1.0.0, pip install dbt was no longer a supported installation method by dbt Labs, and the dbt package on PyPI stopped receiving updates
In fall of 2023, the dbt package on PyPI came back to life as a way to install the dbt Cloud CLI

Additional information

see: #4498 (comment)