[engsys][samples] use the new `import "dotenv/config";` pattern

[jeremymeng]

as it is suggested in dotenv's documentation. https://github.com/motdotla/dotenv/blob/8ab33066f90a20445d3c41e4fafba6c929c5e1a5/README.md#%EF%B8%8F-usage

It would be nice to be consistent across the repository.

[MaryGao]

@jeremymeng does that mean we could replace two lines with only one in sample gen?

From

import * as dotenv from "dotenv";

dotenv.config();

To

import 'dotenv/config';

Do we need to upgrade the dotenv version before that change?

[jeremymeng]

@MaryGao yes, current version (^16.0.0) in the repo should be good. An example:

azure-sdk-for-js/sdk/eventhub/event-hubs/samples-dev/sendEvents.ts

Line 14 in d06725e

import "dotenv/config";