package/gnuplot: bump version to 6.0.3

For release note, see:
http://www.gnuplot.info/ReleaseNotes_6_0_3.html

SHA256 hash now from:
https://sourceforge.net/projects/gnuplot/files/gnuplot/6.0.3/gnuplot-6.0.3.tar.gz.sha256

Signed-off-by: Michael Fischer <mf@go-sys.de>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit 7443e881f8ac86f7c7cbf38c595dbb26f2f66afe)
Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>

package/gnuplot/gnuplot.hash

@@ -1,6 +1,6 @@
-# From https://sourceforge.net/projects/gnuplot/files/gnuplot/6.0.2/
-md5  ea0931758fc180e3b1950931b9869921  gnuplot-6.0.2.tar.gz
-sha1  be803916e4ea32720b4a646f2ffc98d6ad3a0dc2  gnuplot-6.0.2.tar.gz
+# From https://sourceforge.net/projects/gnuplot/files/gnuplot/6.0.3/
+md5  c897ca69062010e2cf5f7483e39e5acc  gnuplot-6.0.3.tar.gz
+sha1  b31779d6760f432f57136600fc0c2bf65f4d4013  gnuplot-6.0.3.tar.gz
+sha256  ec52e3af8c4083d4538152b3f13db47f6d29929a3f6ecec5365c834e77f251ab  gnuplot-6.0.3.tar.gz
 # Locally computed
-sha256  f68a3b0bbb7bbbb437649674106d94522c00bf2f285cce0c19c3180b1ee7e738  gnuplot-6.0.2.tar.gz
 sha256  895928ec0735cca1c8cec42656c7e314a065d0242813bb8693c0c1bf61fd4e4d  Copyright

package/gnuplot/gnuplot.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GNUPLOT_VERSION = 6.0.2
+GNUPLOT_VERSION = 6.0.3
 GNUPLOT_SITE = http://downloads.sourceforge.net/project/gnuplot/gnuplot/$(GNUPLOT_VERSION)
 GNUPLOT_LICENSE = gnuplot license (open source)
 GNUPLOT_LICENSE_FILES = Copyright