package/libxml2: security bump to version 2.11.6

Fix CVE-2023-45322: libxml2 through 2.11.5 has a use-after-free that can
only occur after a certain memory allocation fails. This occurs in
xmlUnlinkNode in tree.c. NOTE: the vendor's position is "I don't think
these issues are critical enough to warrant a CVE ID ... because an
attacker typically can't control when memory allocations fail."

https://gitlab.gnome.org/GNOME/libxml2/-/blob/v2.11.6/NEWS

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit e5af07dce9eb2333a863b09ac1c06eb35f3adb70)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libxml2/libxml2.hash

@@ -1,4 +1,4 @@
-# From https://download.gnome.org/sources/libxml2/2.11/libxml2-2.11.5.sha256sum
-sha256  3727b078c360ec69fa869de14bd6f75d7ee8d36987b071e6928d4720a28df3a6  libxml2-2.11.5.tar.xz
+# From https://download.gnome.org/sources/libxml2/2.11/libxml2-2.11.6.sha256sum
+sha256  c90eee7506764abbe07bb616b82da452529609815aefef423d66ef080eb0c300  libxml2-2.11.6.tar.xz
 # License files, locally calculated
 sha256  c5c63674f8a83c4d2e385d96d1c670a03cb871ba2927755467017317878574bd  Copyright

package/libxml2/libxml2.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 LIBXML2_VERSION_MAJOR = 2.11
-LIBXML2_VERSION = $(LIBXML2_VERSION_MAJOR).5
+LIBXML2_VERSION = $(LIBXML2_VERSION_MAJOR).6
 LIBXML2_SOURCE = libxml2-$(LIBXML2_VERSION).tar.xz
 LIBXML2_SITE = \
 	https://download.gnome.org/sources/libxml2/$(LIBXML2_VERSION_MAJOR)