qt5charts: fix license information
qt5charts-2.1.3 (build with Qt 5.6) doesn't contain any license files so
remove LICENSE.GPL3 from QT5CHARTS_LICENSE_FILES when building Qt 5.6.
Fixes:
http://autobuild.buildroot.net/results/
c95d34129902a0511b8d64c9d50f1ffa293b33fd
http://autobuild.buildroot.net/results/
b9c14ce7c2fdaa412eb6416ae12a0376aaf05770
http://autobuild.buildroot.net/results/
1bde69c515d9140ef0f9a5571475c2850c7b8dee
Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>