Fix wrong RGBA channel mapping when saving OpenEXR.

(cherry picked from commit 08b89a95d2dce9ed663e443c33080f685c37f273)

modules/tinyexr/image_saver_tinyexr.cpp

@@ -171,7 +171,7 @@ Error save_exr(const String &p_path, const Ref<Image> &p_img, bool p_grayscale)
 		{ 0 }, // R
 		{ 1, 0 }, // GR
 		{ 2, 1, 0 }, // BGR
-		{ 2, 1, 0, 3 } // BGRA
+		{ 3, 2, 1, 0 } // ABGR
 	};
 
 	int channel_count = get_channel_count(format);