[libpng] Remove -DPNG_PREFIX=a option when apng feature enabled (#40280)

ports/libpng/portfile.cmake

@@ -1,6 +1,5 @@
 # Download the apng patch
 set(LIBPNG_APNG_PATCH_PATH "")
-set(LIBPNG_APNG_OPTION "")
 if ("apng" IN_LIST FEATURES)
     if(VCPKG_HOST_IS_WINDOWS)
         # Get (g)awk and gzip installed
@@ -25,7 +24,6 @@ if ("apng" IN_LIST FEATURES)
             LOGNAME extract-patch.log
         )
     endif()
-    set(LIBPNG_APNG_OPTION "-DPNG_PREFIX=a")
 endif()
 
 vcpkg_from_github(
@@ -73,7 +71,6 @@ endif()
 vcpkg_cmake_configure(
     SOURCE_PATH "${SOURCE_PATH}"
     OPTIONS
-        ${LIBPNG_APNG_OPTION}
         ${LIBPNG_HARDWARE_OPTIMIZATIONS_OPTION}
         ${LD_VERSION_SCRIPT_OPTION}
         -DPNG_STATIC=${PNG_STATIC}

ports/libpng/vcpkg.json

@@ -1,7 +1,7 @@
 {
   "name": "libpng",
   "version": "1.6.43",
-  "port-version": 2,
+  "port-version": 3,
   "description": "libpng is a library implementing an interface for reading and writing PNG (Portable Network Graphics) format files",
   "homepage": "https://github.com/glennrp/libpng",
   "license": "libpng-2.0",

versions/baseline.json

@@ -4882,7 +4882,7 @@
     },
     "libpng": {
       "baseline": "1.6.43",
-      "port-version": 2
+      "port-version": 3
     },
     "libpopt": {
       "baseline": "1.16",

versions/l-/libpng.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "9c7fd06f1cdd1dfc08b35ca9d6b0ba470cdd2470",
+      "version": "1.6.43",
+      "port-version": 3
+    },
     {
       "git-tree": "915cc8e8e0adbfb2708a310635217811a849d709",
       "version": "1.6.43",