fix: fix miss makezero bug

[alingse]

I was running github actions to run linter makezero for top github golang repos.

see issues alingse/go-linter-runner#1

and the github actions output https://github.com/alingse/go-linter-runner/actions/runs/9242968654/job/25426481866

====================================================================================================
append to slice `metadata` with non-zero initialized length at https://github.com/hashicorp/terraform-provider-google/blob/main/google/services/compute/metadata.go#L[9](https://github.com/alingse/go-linter-runner/actions/runs/9242968654/job/25426481866#step:4:10)8:14
append to slice `old` with non-zero initialized length at https://github.com/hashicorp/terraform-provider-google/blob/main/google/services/compute/resource_compute_subnetwork.go#L354:[10](https://github.com/alingse/go-linter-runner/actions/runs/9242968654/job/25426481866#step:4:11)
append to slice `new` with non-zero initialized length at https://github.com/hashicorp/terraform-provider-google/blob/main/google/services/compute/resource_compute_subnetwork.go#L357:10
====================================================================================================

[github-actions]

** WARNING **: This repository is generated by https://github.com/GoogleCloudPlatform/magic-modules. Any changes made directly to this repository will likely be overwritten. If you have further questions, please feel free to ping your reviewer or, internal employees, reach out to one of the engineers. Thank you!

[SarahFrench]

👋 Hi! As said in the automated message above, this isn't the correct repo to make contributions to. Could you please open a PR in the upstream repo https://github.com/GoogleCloudPlatform/magic-modules with these changes?

The files you'll need to edit in your new PR there are here:

• mmv1/third_party/terraform/services/compute/metadata.go.erb
  
• tpgtools/ignored_handwritten/common_custom_diff.go

[SarahFrench]

As this PR cannot be merged into this repo (it'll be overwritten by any changes coming from the upstream repo) I'm going to close it.

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.