fix user id env variable in ockam-builder docker run cmd

[psinghal20]

Proposed Changes

This PR changes the env variable used in the Ockam-builder docker run command used for building the project.

[mrinalwadhwa]

Hey @psinghal20 changes look great, Thank you for sending the PR ❤️

Before we can merge, a couple of small requests:

1. Could you sign the commit
2. Could you accept our CLA.

Read the CLA at
https://www.ockam.io/learn/how-to-guides/contributing/cla/

To accept the CLA please send a different PR to our contributors repo indicating that you accept the CLA by adding your Git/Github details in a row at the end of the CONTRIBUTORS.csv file:
https://github.com/ockam-network/contributors/blob/master/CONTRIBUTORS.csv

Looking forward to merging your first contribution!!

[psinghal20]

Done! Here is my CLA PR: https://github.com/ockam-network/contributors/pull/17
I have also updated the commit.

[mrinalwadhwa]

Thank you, I merged 7f5d792 after a minor change to the commit message scope based on our conventions.

Congratulations on you first Ockam contribution!! 🎉 🥳