bug#55688: Incorrect documentation of "string-pad"

[emacs--- via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Documentation of "string-pad" function says following (highlighting is
mine).

	@defun string-pad string length &optional padding start

	Pad @var{string} to the be of @var{length} using @var{padding} as the
	padding character (defaulting to the space character).

	If @var{string} is shorter than @var{length}, no padding is done.
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	If @var{start} is @code{nil} (or not present), the padding is done to the
	end of the string, and if it's non-@code{nil}, to the start of the
	string.

=> https://git.savannah.gnu.org/cgit/emacs.git/tree/doc/lispref/strings.texi#n445

I don't think highlighted line is correct. I matches neither behaviour of
emacs:

	=> (string-pad "foo" 12)
	"foo         "

nor what is usually meant by word "padding". I believe issue can be
solved by s/shorter/longer or removing highlighted line at all.