resolves dbt-labs#3578

## What are you changing in this pull request and why?

Two things:
1. Restore ability for users to use `make run` and `make build` to
preview/build the docs site while developing locally.
2. Align with the goal in
dbt-labs#3284 to remove
generation of redirects from the Makefile.

## Outstanding questions

### Question 1
The pull request template says the following:
```
- [ ] [Ran link testing](https://github.com/dbt-labs/docs.getdbt.com#running-the-cypress-tests-locally) to update the links that point to the deleted page
```

I'm assuming this is the most up-to-date approach for link testing? I
haven't used it personally yet, so I don't know 🤷

### Question 2

After the changes within this PR, there are no longer any references to
any `make` commands within our README. Do we want to add them anywhere
as an alternative method to running the `npm` commands directly?

## Checklist
- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
and [About
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
so my content adheres to these guidelines.
- [x] Remove unnecessary parts of Makefile
- [x] Add @JKarlavige as a reviewer ("needs technical review")