Fix naming inconsistency of VPN data sources

[guineveresaenger]

There's a few namespace typos in the VPN data sources: https://github.com/pulumi/pulumi-alicloud/blob/master/provider/resources.go#L2070

We should fix these.

This will also constitute a breaking change so we'll need to cut a release with appropriate notes.

[iwahbe]

@guineveresaenger Can you point out the naming inconsistencies with a perma-link? I can't find any on master.

[github-actions]

Unfortunately, it looks like this issue hasn't seen any updates in a while. If you're still experiencing this issue, could you leave a quick comment to let us know so we can prioritize it?