chore: fix dependabot errors

[doherty100]

Purpose

• Fix dependabot version errors

Does this introduce a breaking change?

[ ] Yes
[ X ] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ X ] Other... Please describe: depandabot configuration changes

How to Test

• Provision a new sandbox environment
• Run unit tests

What to Check

Verify that the following are valid

• Unit tests should all pass.

Other Information

[doherty100]

Root-cause analysis: why this change was needed

Summary

Nothing changed in this repo's dependabot.yml or on the Terraform side. A Dependabot service update on 2026-07-13 tightened config validation and began rejecting the long-tolerated, Terraform-unsupported versioning-strategy key, which silently killed that week's update run. Removing the key (this PR) restores normal operation.

Timeline (from this repo's Dependabot PR history)

versioning-strategy: increase was present on all terraform jobs the whole time (added 2026-03-26 in #260, "chore: update terraform providers" — undocumented/incidental), yet weekly grouped PR batches ran fine every Monday:

Scheduled Monday	Dependabot PRs opened
2026-06-08	4 (#441–#444)
2026-06-15	14 (#449–#462)
2026-06-22	14 (#476–#489)
2026-06-29	14 (#502–#515)
2026-07-06	14 (#528–#541)
2026-07-13	0 — first missed run in the entire history
2026-07-14	this PR (#555) removes versioning-strategy

The last successful automated batch (#528–#541, azurerm ~> 4.79.0 → ~> 4.80.0) was created with the key still present, confirming it was harmless/tolerated for months.

What actually changed

• versioning-strategy is ecosystem-gated and has never been supported for the terraform ecosystem (it's still being rolled out per-ecosystem upstream — e.g. dependabot-core v0.386.0 added it for helm in helm: support versioning-strategy (range-preserving updates) dependabot/dependabot-core#15218).
• Upstream config-parser hardening landed in dependabot-core v0.383.0 (2026-06-24) and v0.384.0 (2026-06-30) (e.g. Type the Dependabot config file parser dependabot/dependabot-core#15401 "Type the Dependabot config file parser"), moving validation toward fail-fast on unsupported keys.
• The break date (2026-07-13) lands exactly on the publish of dependabot-core v0.386.0 (2026-07-13). When GitHub's hosted Dependabot picked up the stricter validation, the unsupported versioning-strategy on terraform now rejects the whole config, so no PRs were generated.

Caveat

There is no public GitHub changelog entry or REST endpoint stating "terraform now rejects versioning-strategy" — that validation is enforced server-side and the literal error only renders on the repo's Insights → Dependency graph → Dependabot page. The evidence here is behavioral (14 PRs every Monday for months → 0 on the exact day v0.386.0 shipped → manual key removal the next day), but it is conclusive.

Net effect of this PR

No change to how Terraform updates are proposed (the key was inert for terraform); it only removes the config-validation failure that had stopped the weekly runs.