[Docs] Mention eksctl anywhere tool will ask the vCenter will import the OVA from Internet

**What would you like to be added**:
In the docs, it could have been mentioned that `eksctl anywhere` tool will ask the vCenter to download the OVA from the Internet automatically.

**Why is this needed**:
Without such information, the user might guess that the `eksctl anywhere` tool will download the OVA file from the internet to the workstation and upload to the vCenter. On the other hand, if vCenter does not have Internet access, it will return a 500 error in the debug logs which confuses the user.

Locate the eksctl anywhere documentation describing vCenter OVA import behavior. Add a clear note that vCenter downloads the OVA from the Internet and explain that lacking vCenter Internet access can produce a 500 error in debug logs. Done means users understand where the download occurs and the required connectivity.

Written by the indexing model from the issue text.