package/gstreamer1/gstreamer1-editing-services: disable introspection

Disable introspection as it raises a build failure with autotools.
It could be enabled after bumping to upcoming 1.18.x and switching to
messon. We can't switch now as version 1.16.2 don't allow to disable
examples/tools through meson

Fixes:
 - http://autobuild.buildroot.org/results/36eb875fba2847b32df05f31d8f8ca9f0ecde36f



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>