Provider check does not support registry.opentofu.org

### tf-migrate version

commit caa64b3

### Migration path

v4 to v5

### Affected resource type(s)

_No response_

### Description

Version doesn't recognise the Opentofu provider repository. Workaround is to use `--skip-version-check`

### Input configuration

```hcl
n/a
```

### Expected output

```hcl

```

### Actual output

```shell
Error: no Cloudflare provider found in .terraform.lock.hcl
```

### Steps to reproduce

tf-migrate migrate --source-version v4 --target-version v5

### Additional context

_No response_

Run `tf-migrate migrate --source-version v4 --target-version v5` against a configuration using the OpenTofu provider and inspect how `.terraform.lock.hcl` is checked. The work is done when `registry.opentofu.org` is recognized and the migration no longer requires `--skip-version-check`.

Written by the indexing model from the issue text.