package/libgdiplus: bump to version 6.1

- bump to version 6.1
- updated makefile to download source from
  https://download.mono-project.com/sources/libgdiplus/
  instead of github to avoid submodule build error
  from ./update_submodules.sh

Signed-off-by: Kalpesh Panchal <kalpesh.panchal2@collins.com>
Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libgdiplus/libgdiplus.hash

@@ -1,3 +1,3 @@
 # Locally computed:
-sha256  1fd034f4b636214cc24e94c563cd10b3f3444d9f0660927b60e63fd4131d97fa  libgdiplus-6.0.5.tar.gz
+sha256  97d5a83d6d6d8f96c27fb7626f4ae11d3b38bc88a1726b4466aeb91451f3255b  libgdiplus-6.1.tar.gz
 sha256  81317bf837e02a116dc20b032fa1d0cbf9ec357621f141ff2c2daf26c17cbb5d  LICENSE

package/libgdiplus/libgdiplus.mk

@@ -4,8 +4,8 @@
 #
 ################################################################################
 
-LIBGDIPLUS_VERSION = 6.0.5
-LIBGDIPLUS_SITE = $(call github,mono,libgdiplus,$(LIBGDIPLUS_VERSION))
+LIBGDIPLUS_VERSION = 6.1
+LIBGDIPLUS_SITE = https://download.mono-project.com/sources/libgdiplus
 
 LIBGDIPLUS_LICENSE = MIT
 LIBGDIPLUS_LICENSE_FILES = LICENSE