Remove artifact repository beta URL, fixup handwritten tests

[modular-magician]

Fixes b/270298939

Seems like this service declined to update its beta API, meaning the invariant that beta APIs are a superset of GAs is broken. The test configuration here succeeds on the GA provider but fails on the beta one:

│ Error: Error creating Repository: googleapi: Error 400: Invalid value at 'repository.format' (type.googleapis.com/google.devtools.artifactregistry.v1beta2.Repository.Format), "KFP"
│ Details:
│ [
│   {
│     "@type": "type.googleapis.com/google.rpc.BadRequest",
│     "fieldViolations": [
│       {
│         "description": "Invalid value at 'repository.format' (type.googleapis.com/google.devtools.artifactregistry.v1beta2.Repository.Format), \"KFP\"",
│         "field": "repository.format"
│       }
│     ]
│   }
│ ]
│
│   on main.tf line 1, in resource "google_artifact_registry_repository" "my-repo":
│    1: resource "google_artifact_registry_repository" "my-repo" {

Also rename some tests to match standard format, un-guard the handwritten test file.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Generated Terraform providers, and ran make test and make lint in the generated providers to ensure it passes unit and linter tests.
• Ran relevant acceptance tests using my own Google Cloud project and credentials (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

artifactregistry: fixed an issue where `google-beta` used an outdated beta API rather than the GA service API. New format values like "KFP" will now be accepted by both providers.

Derived from GoogleCloudPlatform/magic-modules#7345