Outdated api versions returned for Microsoft.Resources/resourceGroups

[REST](https://docs.microsoft.com/en-us/rest/api/resources/providers/get) response doesn't include the latest available api versions for Microsoft.Resources/resourceGroups

current:
```json
{
"resourceType": "resourceGroups",
"apiVersions": [
"2019-05-01",
"2019-04-01",
"2019-03-01",
"2018-11-01",
"2018-09-01",
"2018-08-01",
"2018-07-01",
...
]
}
```
expected:
```json
{
"resourceType": "resourceGroups",
"apiVersions": [
"2021-04-01",
"2021-01-01",
....
]
}
```

Start with the Microsoft.Resources provider REST endpoint linked in the issue and inspect how its resourceGroups apiVersions response is sourced. Update the specification data so the response includes the latest versions shown in the expected example, then verify that the endpoint no longer returns only the older versions.

Written by the indexing model from the issue text.