fix: '3-networks' minor inconsistencies and typos

[vovinacci]

This PR fixes 3-networks minor inconsistencies, typos and copy-pastas.

Closes #294

[vovinacci]

@rjerrems @bharathkkb Integration test failed, checked the test spec - didn't find anything that may have broken by this PR. As I don't have access to cloud build for this project, could you please take a look on what it failed? Much appreciated.

[rjerrems]

/gcbrun

[rjerrems]

I had a look and triggered the test again, it looks like we hit a transient issue on both. First was a concurrent operation updating IAM on billing project and second was a clash in terms of project names.

@bharathkkb - Did we modify the prefix already? Is that only on develop?

For now I have triggered another test run

[vovinacci]

@rjerrems Thanks much! Seems to be fine now.

[rjerrems]

This should stay as Base as per page 30 of the security foundation guide here https://services.google.com/fh/files/misc/google-cloud-security-foundations-guide.pdf

[rjerrems]

Thanks @vovinacci - I have one small nit for a comment, but once that's fixed it LGTM

[vovinacci]

@rjerrems Thanks a lot for the review. Reverted back to Base, also amended for other environments, so the naming is consistent.

[rjerrems]

LGTM

@bharathkkb FYI