DocBook: Cleanup: remove an unused $(call) line

There's no build_images function to call. So remove it.

This is just a cleanup patch, with doesn't affect the build.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
1 file changed