Fix GCE terraform region/zone for light stemcell CI pipeline

[Alphasite]

Summary

Two fixes to unblock the failing `create-light-google-ubuntu-jammy-1` CI build #16:

1. Add explicit GCE region/zone — `light-google-environment-oss` terraform resource in `ci/pipeline-template.yml` was defaulting to `us-central1-f`, which returned "does not have enough resources available to fulfill the request (resource type: compute)". Switched to `europe-north2` / `europe-north2-a`.

2. Switch machine type `n1-standard-2` → `e2-standard-2` — N1 machine types are not available in `europe-north2` at all. `e2-standard-2` is the equivalent (2 vCPU, 8 GB) and is supported across all `europe-north2` zones.

Files changed

File	Change
`ci/pipeline-template.yml`	Add `gce_region: europe-north2`, `gce_zone: europe-north2-a` to terraform vars
`ci/tasks/light-google/skeletal-deployment.yml`	`machine_type: n1-standard-2` → `e2-standard-2`

Jira: TNZ-119889 / TNZ-116382

Test plan

• Re-run `create-light-google-ubuntu-jammy-1` pipeline job to confirm it passes

[coderabbitai]

Walkthrough

The light-google-environment-oss Terraform resource now sets gce_region to europe-north2 and gce_zone to europe-north2-a in its source.vars configuration.

Suggested reviewers: copilot, aramprice, ystros

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description covers the change, but it omits the required merge-forward note and the AI review feedback section from the template.	Add the merge-forward instructions and an AI Review Feedback section, including how each outstanding review comment was resolved.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: fixing the GCE region/zone for the light stemcell CI pipeline.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch tnz-116382-fix-gce-region-europe-north2

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[Copilot]

Pull request overview

Updates the Concourse pipeline template so the GCE terraform resource used for building light stemcells targets the intended Europe North 2 region/zone, avoiding Terraform falling back to us-central1 defaults and breaking the light stemcell CI flow.

Changes:

• Adds gce_region: europe-north2 and gce_zone: europe-north2-a to the light-google-environment-oss terraform resource vars.

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