Bump libxml2 to v2.13.4 (#2489)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e6e4f9..aedfccc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,7 @@
 * Write an empty HandlerBox name field instead of "libavif" (saves 7 bytes).
 * Update aom.cmd/LocalAom.cmake: v3.10.0
 * Update avm.cmd: research-v8.0.0
+* Update libxml2.cmd/LocalLibXml2.cmake: v2.13.4
 * Update svt.cmd/svt.sh/LocalSvt.cmake: v2.2.1
 * Change experimental gainmap API: remove avifGainMapMetadata and
   avifGainMapMetadataDouble structs.
diff --git a/cmake/Modules/LocalLibXml2.cmake b/cmake/Modules/LocalLibXml2.cmake
index 64f90a6..894c485 100644
--- a/cmake/Modules/LocalLibXml2.cmake
+++ b/cmake/Modules/LocalLibXml2.cmake
@@ -1,4 +1,4 @@
-set(AVIF_LOCAL_LIBXML_GIT_TAG "v2.12.7")
+set(AVIF_LOCAL_LIBXML_GIT_TAG "v2.13.4")
 
 set(LIB_FILENAME "${AVIF_SOURCE_DIR}/ext/libxml2/install.libavif/lib/${AVIF_LIBRARY_PREFIX}xml2${CMAKE_STATIC_LIBRARY_SUFFIX}")
 if(EXISTS "${LIB_FILENAME}")
@@ -31,7 +31,7 @@
 
     FetchContent_Declare(
         libxml2
-        GIT_REPOSITORY "https://gitlab.gnome.org/GNOME/libxml2.git"
+        GIT_REPOSITORY "https://github.com/GNOME/libxml2.git"
         BINARY_DIR "${LIBXML2_BINARY_DIR}"
         GIT_TAG "${AVIF_LOCAL_LIBXML_GIT_TAG}"
         GIT_SHALLOW ON
diff --git a/ext/libxml2.cmd b/ext/libxml2.cmd
index 9ce7d6d..27ea148 100755
--- a/ext/libxml2.cmd
+++ b/ext/libxml2.cmd
@@ -5,7 +5,7 @@
 
 : # libxml2 is released under the MIT License.
 
-git clone -b v2.12.7 --depth 1 https://gitlab.gnome.org/GNOME/libxml2.git
+git clone -b v2.13.4 --depth 1 https://github.com/GNOME/libxml2.git
 
 mkdir -p libxml2/build.libavif
 cmake libxml2 -B libxml2/build.libavif/ -G Ninja -DBUILD_SHARED_LIBS=OFF -DCMAKE_INSTALL_PREFIX=libxml2/install.libavif \