tools: gst-inspect: don't print internal pad request function name

tools: gst-inspect: don't print internal pad request function name

This just confuses people, they look at it and try to call it
directly by name, instead of using the public GstElement API.
It stands to reason that it goes without saying that when an
element provides request pads that they can actually be
requested using the standard API, and there's no point in
printing internal implementation details of the element.