Revert "package/libpng: bump version to 1.6.44"

This reverts commit 6f22278527c15e8944c0bdc819a023355cc2c001.

Libpng 1.6.44 triggers a number of autobuilder issues on arm(eb), E.G.:

http://autobuild.buildroot.net/results/72af84420ebdae8cb10c6988312e50268583a427/
http://autobuild.buildroot.net/results/e4c0e3685ffc63a2c6ffa4f60e4ed6ffdd81deea/

The "fixes and improvements" in 1.6.44 are not strictly needed for
2024.02.x, so go back to 1.6.43 instead.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libpng/libpng.hash

@@ -1,4 +1,4 @@
-# From https://sourceforge.net/p/png-mng/mailman/message/58815959/
-sha256  60c4da1d5b7f0aa8d158da48e8f8afa9773c1c8baa5d21974df61f1886b8ce8e  libpng-1.6.44.tar.xz
+# From https://sourceforge.net/p/png-mng/mailman/message/58741099/
+sha256  6a5ca0652392a2d7c9db2ae5b40210843c0bbc081cbd410825ab00cc59f14a6c  libpng-1.6.43.tar.xz
 # Locally computed:
 sha256  7317e078e2d3b5d7ba5a6159e650945153262b44b76f6700f8e9edb261c5143e  LICENSE

package/libpng/libpng.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-LIBPNG_VERSION = 1.6.44
+LIBPNG_VERSION = 1.6.43
 LIBPNG_SERIES = 16
 LIBPNG_SOURCE = libpng-$(LIBPNG_VERSION).tar.xz
 LIBPNG_SITE = http://downloads.sourceforge.net/project/libpng/libpng$(LIBPNG_SERIES)/$(LIBPNG_VERSION)