mark removed fields as computed

[danawillow]

As per guidelines at https://www.terraform.io/docs/extend/best-practices/deprecations.html.

Fixes hashicorp/terraform-provider-google#5265.

Release Note Template for Downstream PRs (will be copied)

all: fixed issue where many fields that were removed in 3.0.0 would show a diff when they were removed from config

[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, cd13a00.

Pull request statuses

WARNING: The following files changed in commit cd13a00 may need corresponding changes in third_party/validator:

• third_party/terraform/resources/resource_storage_bucket.go

No diff detected in terraform-google-conversion.
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#1585
depends: hashicorp/terraform-provider-google#5313
depends: ansible-collections/google.cloud#121

[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, e5a4078.

Pull request statuses

WARNING: The following files changed in commit e5a4078 may need corresponding changes in third_party/validator:

• third_party/terraform/resources/resource_storage_bucket.go

terraform-provider-google-beta already has an open PR.
No diff detected in terraform-google-conversion.
terraform-provider-google already has an open PR.
No diff detected in Ansible.
No diff detected in Inspec.

New Pull Requests

I didn't open any new pull requests because of this PR.