package/imagemagick: remove useless makefile target.

Makefile's target "install-magickincarchHEADERS" and "magick-install-data-local"
install both the same file (magick-baseconfig.h) in the same time...

The problem can be reproduced with:
mkdir /tmp/bar
/usr/bin/install -c -m 644 foo /tmp/bar &
/usr/bin/install -c -m 644 foo /tmp/bar/foo
/usr/bin/install: cannot create regular file '/tmp/bar/foo' : File exists

So, remove one of them.

Fixes:
http://autobuild.buildroot.net/results/d34/d34077ce582866c50bbd90de10bbe593e39463f1/build-end.log



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>