Update libpng to 1.6.56 (#9499)

Author: radarhere

.github/workflows/wheels-dependencies.sh

@@ -92,7 +92,7 @@ ARCHIVE_SDIR=pillow-depends-main
 # Package versions for fresh source builds.
 FREETYPE_VERSION=2.14.3
 HARFBUZZ_VERSION=13.2.1
-LIBPNG_VERSION=1.6.55
+LIBPNG_VERSION=1.6.56
 JPEGTURBO_VERSION=3.1.3
 OPENJPEG_VERSION=2.5.4
 XZ_VERSION=5.8.2

winbuild/build_prepare.py

@@ -121,7 +121,7 @@ def cmd_msbuild(
     "LCMS2": "2.18",
     "LIBAVIF": "1.4.1",
     "LIBIMAGEQUANT": "4.4.1",
-    "LIBPNG": "1.6.55",
+    "LIBPNG": "1.6.56",
     "LIBWEBP": "1.6.0",
     "OPENJPEG": "2.5.4",
     "TIFF": "4.7.1",