improve comment

Author: Yay295

Tests/test_file_tiff.py

@@ -109,7 +109,7 @@ def test_bigtiff(self, tmp_path: Path) -> None:
 
         with Image.open("Tests/images/hopper_bigtiff.tif") as im:
             # The data type of this file's StripOffsets tag is LONG8,
-            # which is not currently supported when saving.
+            # which is not yet supported for offset data when saving multiple frames.
             del im.tag_v2[273]
 
             outfile = str(tmp_path / "temp.tif")