ARM JSON template linter rejects current apiVersions

### Bug description

Opening a raw ARM JSON templateand setting a resource's `apiVersion` to a current Azure API version triggers a linter error saying the value isn't accepted.

Example: `Microsoft.Network/virtualNetworks` with `"apiVersion": "2023-09-01"` (a real, documented Azure API version) is flagged with:

> Value is not accepted. Valid values: "2017-06-01".

Same happens for the corresponding `Microsoft.Network/virtualNetworks/subnets` resource.

extension version `0.46.1`

### To reproduce

1. Install `ms-azuretools.vscode-bicep`
2. Open/create a `.json` ARM template with:
```json
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {},
"variables": {},
"resources": [
{
"type": "Microsoft.Network/virtualNetworks",
"apiVersion": "2023-09-01",
"name": "exampleVnet",
"location": "eastus",
"properties": {
"addressSpace": { "addressPrefixes": ["10.20.0.0/16"] }
}
}
]
}
```
3. Observe the linter warning/error on the `apiVersion` line: "Value is not accepted. Valid values: "2017-06-01"."

### Expected behavior

The linter's apiVersion allowlist for a given resource type should reflect apiVersions that are current.

### Actual behavior

The linter rejects valid, current apiVersions and only accepts very old ones, suggesting the bundled azure-resource-manager-schemas snapshot used for ARM JSON template validation is stale relative to the extension's own release cadence.

### Additional context

A near-identical bug was reported years ago against the predecessor extension, `microsoft/vscode-azurearmtools#255` ("Latest API version not supported"), which described the exact same symptom ("Valid values: '2017-06-01'") for a different resource type. That repo/extension is now archived and superseded by this one (`ms-azuretools.vscode-bicep`, which also lints raw ARM JSON templates), and the underlying stale-schema behavior appears to have carried over rather than being fixed.

### Environment

- Extension: `ms-azuretools.vscode-bicep` v0.46.1 (Marketplace-listed release date 2026-08-31)
- VS Code, Windows 11

Start with the ARM JSON template linter and the bundled azure-resource-manager-schemas snapshot used for validation. Reproduce the warning with Microsoft.Network/virtualNetworks and apiVersion 2023-09-01, then trace how the snapshot supplies allowed versions. Done means current documented versions are accepted, including the virtualNetworks/subnets case, with regression coverage for the example.

Written by the indexing model from the issue text.