Added note about ppg-tunnel automatically picking up DATABASE_URL from env file (#6782)

* Added note about env file automatically picking up env

* Update 600-tcp-tunnel.mdx

Co-authored-by: Jon Harrell <[email protected]>

---------

Co-authored-by: Jon Harrell <[email protected]>

Author: nurul3101

content/250-postgres/600-tcp-tunnel.mdx

@@ -23,7 +23,7 @@ While in Early Access, usage of the TCP tunnel will be free of charge.
 
 ### Exporting environment variables
 
-The tunnel expects you to have the following `DATABASE_URL` environment variable set to the connection URL of your Prisma Postgres instance.
+The tunnel expects you to have the following `DATABASE_URL` environment variable set to the connection URL of your Prisma Postgres instance. If you are running the tunnel command from your project where an `.env` file has `DATABASE_URL` already set, you can skip this step as the tunnel will automatically pick it up.
 
 To export the `DATABASE_URL` environment variable temporarily in a terminal session: