Explicitly call out PSC NEG for deployment setup

[puneetsarna]

GCP has various types of NEG and the one we care
about is the PSC NEG that enables the customer to
connect to a service provider via the service
attachment.

Proposed changes

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[puneetsarna]

@JTorreG

[amudukutore]

Minor comment, looks good otherwise.