Looks like the bintray publish_wait_for_secs was being ignored because the
content type wasn't being set, so it defaulted to x-www-form-urlencoded
instead of application/json.

Changes the  timeout to 0 to preserve current non-blocking behavior, which
we want in case multiple formulae are being updated.

Closes Homebrew/homebrew#49951.

Signed-off-by: Andrew Janke <andrew@apjanke.net>