Fix the API comment about `png_data_freer`

The old note about this function being unlikely to work correctly was
likely incorrect.
diff --git a/png.c b/png.c
index f019394..0dbb234 100644
--- a/png.c
+++ b/png.c
@@ -447,7 +447,6 @@
    memset(info_ptr, 0, (sizeof *info_ptr));
 }
 
-/* The following API is not called internally */
 void PNGAPI
 png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
     int freer, png_uint_32 mask)
diff --git a/png.h b/png.h
index b650379..f0f4560 100644
--- a/png.h
+++ b/png.h
@@ -1730,12 +1730,9 @@
 PNG_EXPORT(98, void, png_free_data, (png_const_structrp png_ptr,
     png_inforp info_ptr, png_uint_32 free_me, int num));
 
-/* Reassign responsibility for freeing existing data, whether allocated
+/* Reassign the responsibility for freeing existing data, whether allocated
  * by libpng or by the application; this works on the png_info structure passed
- * in, it does not change the state for other png_info structures.
- *
- * It is unlikely that this function works correctly as of 1.6.0 and using it
- * may result either in memory leaks or double free of allocated data.
+ * in, without changing the state for other png_info structures.
  */
 PNG_EXPORT(99, void, png_data_freer, (png_const_structrp png_ptr,
     png_inforp info_ptr, int freer, png_uint_32 mask));