Remove inline JS script

[hgtonight]

Gdn_Controller provides an InformMessage() method.

[bleistivt]

That would make it nice and short, but it's not really the same.
The intention is for the message to pop up only if a users focuses the comment form (so it draws immediate attention). If the message is always there, people get used to it and may ignore it.

When 2.2 is released changing this to use Head->AddScript() will be cleaner.

[hgtonight]

Oh wow.

I feel like an idiot. I didn't even notice the on focus.

I still have an idea that would make it "cleaner". Will post to this branch.