Clarifications about running dbt init --profile (#4534)

Clarifications about running dbt init --profile

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

-Clarify the use of `dbt init` when using an existing `profiles.yml`
file. The current docs are not clear enough and one may think you have
to provide the path to `profiles.yml` as an argument, for example, `dbt
init --profile profiles.yml` when, in fact, you need to pass the actual
name of your profile.

<br>

**REMOVED CHANGES:**

-~~Clarify that you cannot pass the `--profile` flag if you already have
a dbt_project.yml file as the error returned (`Can not init existing
project with specified profile, edit dbt_project.yml instead`) may be
confusing~~


-~~Change VersionBlock version from 1.7 to 1.8~~

## Checklist

- [X] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
so my content adheres to these guidelines.

- [X] For [docs
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#about-versioning),
review how to [version a whole
page](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
and [version a block of
content](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#versioning-blocks-of-content).

- [X] Add a checklist item for anything that needs to happen before this
PR is merged, such as "needs technical review" or "change base branch."

- [X] Need review of the doc changes as this is my first contribution

website/docs/reference/commands/init.md

@@ -19,7 +19,7 @@ Then, it will:
 
 <VersionBlock firstVersion="1.7">
 
-When using `dbt init` to initialize your project, include the `--profile` flag to specify an existing `profiles.yml` as the `profile:` key to use instead of creating a new one. For example, `dbt init --profile`.
+When using `dbt init` to initialize your project, include the `--profile` flag to specify an existing `profiles.yml` as the `profile:` key to use instead of creating a new one. For example, `dbt init --profile profile_name`.