Android buildsystem: Drop obsolete NDK_TOOLCHAIN argument

It was a duplicate of NDK_TARGET, and not used for anything.

platform/android/detect.py

@@ -21,7 +21,6 @@ def get_opts():
 
 	return [
 			('ANDROID_NDK_ROOT', 'the path to Android NDK', os.environ.get("ANDROID_NDK_ROOT", 0)),
-			('NDK_TOOLCHAIN', 'toolchain to use for the NDK',"arm-eabi-4.4.0"),
 			('NDK_TARGET', 'toolchain to use for the NDK',os.environ.get("NDK_TARGET", "arm-linux-androideabi-4.9")),
 			('NDK_TARGET_X86', 'toolchain to use for the NDK x86',os.environ.get("NDK_TARGET_X86", "x86-4.9")),
 			('ndk_platform', 'compile for platform: (android-<api> , example: android-15)',"android-15"),