Implementation on TRUNCATE is incorrect

Shaun McVey (smcvey) commented:

https://www.cockroachlabs.com/docs/stable/truncate.html

At the top of this page is the following sentence:

```
The TRUNCATE statement removes all rows from a table. At a high level, it works by dropping the table and recreating a new table with the same name.
```

The second sentence (about dropping the table and recreating) has not been true since 20.2.

Suggest the sentence is removed or replace with a correct description of what happens (You would need to check with the SQL Schema team for a good sentence).

Jira Issue: DOC-2133