Context: #6491

For this command, we moved to a new API which requires us to specify a URL of which home site you want to remove. The current API request fails when the user has multiple home sites configured.
Therefore we should make option url required and get rid of all the legacy code (code branch that is executed when the user doesn't specify option url).

Let's:

spo homesite remove:

• Make option url required.
• Remove the legacy command code where we use the old API (without URL).
• Remove the output of the command (the current output doesn't add much value).

spo homesite get:

• Update the description so it's clear the command is to retrieve an existing home site
• Add option --url <url> which is required
• Use a new endpoint that works with multiple home sites