Fix google_project default network deletion by correcting URL

[rileykarson]

Fixes hashicorp/terraform-provider-google#4746

Fixing the tests I broke last week and noticed this one was a real failure. Enforcer conditioned me too well to ignore errors when firewalls were attached to networks 🤦‍♀

Release Note Template for Downstream PRs (will be copied)

`resourcemanager`: fixed deleting the default network in `google_project`

[modular-magician]

Hi! I'm the modular magician, I work on Magic Modules.
I see that this PR has already had some downstream PRs generated. Any open downstreams are already updated to your most recent commit, b11b640.

Pull request statuses

WARNING: The following files changed in commit b11b640 may need corresponding changes in third_party/validator:

• third_party/terraform/resources/resource_google_project.go

No diff detected in terraform-google-conversion.
No diff detected in Ansible.
No diff detected in Inspec.

New Pull Requests

I built this PR into one or more new PRs on other repositories, and when those are closed, this PR will also be merged and closed.
depends: hashicorp/terraform-provider-google-beta#1299
depends: hashicorp/terraform-provider-google#4748

[callppatel]

We started getting error since yesterday in our terraform module to create project. We delete default n/w in our terraform module. @rileykarson - We suspect this could be some recent change implemented. Our error message is

google_project.project: Error deleting default network in project sbx-5064-test-project-07f972cf: Error waiting for Deleting Network: The network resource 'projects/sbx-zzzzz/global/networks/default' is already being used by 'projects/sbx-zzzzz/global/firewalls/default-allow-icmp'

[rileykarson]

Yes- that's the error this fixes. See the linked issue at hashicorp/terraform-provider-google#4746.