webos-preferred-versions: Fix entry for libsoup-2.4

:Release Notes:
libsoup-2.4 recipe is provided by meta-webos layer, so the recipe
here is used by default and PREFERRED_VERSION isn't really needed.

:Detailed Notes:
meta-webos supplies PREFERRED_VERSION_libsoup = "2.40.3", but the
actual package name is "libsoup-2.4", so it should read
PREFERRED_VERSION_libsoup-2.4 = "2.40.3".

:Testing Performed:
Only build tested - nothing was changed.

:QA Notes:
No change in image.

:Issues Addressed:
[GF-11453] libsoup-2.4 PREFERRED_VERSION not set properly in meta-webos

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ifca3cb6ecf24697df7f66f30f3de5f20f613acfa
Reviewed-on: https://g2g.palm.com/3162
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>