pil_codec - fix decoder typing issue

Author: K0lb3

Diff for: astc_encoder/pil_codec.py

@@ -4,7 +4,7 @@
 """
 
 import struct
-from typing import Any, List
+from typing import Any, List, Union
 
 from PIL import Image, ImageFile
 
@@ -100,7 +100,9 @@ def init(self, args: List[Any]):  # noqa: D102
         )
         self.context = ASTCContext(config)
 
-    def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:  # noqa: D102
+    def decode(
+        self, buffer: Union[bytes, Image.SupportsArrayInterface]
+    ) -> tuple[int, int]:  # noqa: D102
         assert self.state.xoff == 0 and self.state.yoff == 0, "Cannot handle offsets"
 
         config = self.context.config