package/gobject-introspection: fix gidatadir

Since commit 521d3876 gidatadir is
wrongly set to ${libdir}/../share, set it back to
${datadir}/gobject-introspection-1.0

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