package/libxml2: security bump to version 2.13.8

Fixes the following security vulnerabilities:

[CVE-2025-32414] Buffer overflow when parsing text streams with Python API
https://gitlab.gnome.org/GNOME/libxml2/-/issues/889

[CVE-2025-32415] Heap-based Buffer Overflow in xmlSchemaIDCFillNodeTables
https://gitlab.gnome.org/GNOME/libxml2/-/issues/890

https://www.openwall.com/lists/oss-security/2025/04/17/3

For release notes since 2.13.6, see:
https://download.gnome.org/sources/libxml2/2.13/libxml2-2.13.7.news
https://download.gnome.org/sources/libxml2/2.13/libxml2-2.13.8.news

Signed-off-by: Christian Hitz <christian.hitz@bbv.ch>
[Julien: add links to release notes]
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/libxml2/libxml2.hash

@@ -1,4 +1,4 @@
-# From https://download.gnome.org/sources/libxml2/2.13/libxml2-2.13.6.sha256sum
-sha256  f453480307524968f7a04ec65e64f2a83a825973bcd260a2e7691be82ae70c96  libxml2-2.13.6.tar.xz
+# From https://download.gnome.org/sources/libxml2/2.13/libxml2-2.13.8.sha256sum
+sha256  277294cb33119ab71b2bc81f2f445e9bc9435b893ad15bb2cd2b0e859a0ee84a  libxml2-2.13.8.tar.xz
 # License files, locally calculated
 sha256  c99aae1afe013e50b8b3701e089222b351258043c3025b64053a233fd25b4be7  Copyright

package/libxml2/libxml2.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 LIBXML2_VERSION_MAJOR = 2.13
-LIBXML2_VERSION = $(LIBXML2_VERSION_MAJOR).6
+LIBXML2_VERSION = $(LIBXML2_VERSION_MAJOR).8
 LIBXML2_SOURCE = libxml2-$(LIBXML2_VERSION).tar.xz
 LIBXML2_SITE = \
 	https://download.gnome.org/sources/libxml2/$(LIBXML2_VERSION_MAJOR)