Fixed incorrect CMake variable for MACOSX_BUNDLE in expat and libpng libraries

Signed-off-by: lumberyard-employee-dm <[email protected]>

package-system/expat/build_config.json

@@ -69,7 +69,7 @@
             "cmake_generate_args": [
                 "-G",
                 "Xcode",
-                "-DDCMAKE_MACOSX_BUNDLE=OFF",
+                "-DCMAKE_MACOSX_BUNDLE=OFF",
                 "-DCMAKE_TOOLCHAIN_FILE=../../../../Scripts/cmake/Platform/iOS/Toolchain_ios.cmake"
             ],
             "custom_test_cmd" : [

package-system/libpng/build_config.json

@@ -71,7 +71,7 @@
                 "cmake_generate_args_release": [
                     "-G",
                     "Xcode",
-                    "-DDCMAKE_MACOSX_BUNDLE=OFF",
+                    "-DCMAKE_MACOSX_BUNDLE=OFF",
                     "-DCMAKE_TOOLCHAIN_FILE=../../../../Scripts/cmake/Platform/Mac/Toolchain_mac.cmake",
                     "-T",
                     "buildsystem=1"