Change description of signup_available_signups view

stBorchert pointed out in IRC that the current description for this view is a little unwieldy:

"A view of all available signups (signup-enabled content the user has not replied to)."

How about this?

"A view of all open signups the user hasn't replied to."

I like the "has not replied to" part, since that's a key feature of this view, but it's late and I'm not feeling sure of myself to just commit this one, so if anyone else has ideas, please comment here. ;)

Thanks,
-Derek