Unnecessary `vhs publish` message

[rm-dr]

trafficstars

There's no reason to show users the Host your GIF on vhs.charm.sh... message every single time vhs is run.

• People that will use vhs publish don't need this message, they'll likely discover this feature in the docs or help text.
  If they don't read the docs, they're doomed anyway.
• People that won't use vhs publish really don't need this message.

Showing this message on the first run of vhs would make sense, but that involves keeping state and is probably more trouble than it's worth.

So, I propose we remove that message altogether, and instead rely on the documentation and on vhs --help.

[maaslalani]

You can hide the hint/message with by setting VHS_PUBLISH=false.

We'll also likely remove the hint in the future.

[bashbunni]

I think we can remove this once we add the info for vhs publish to our docs 👍