Fix #1095 by correcting ContextBlock element type hint (#1096)

Author: seratch

slack_sdk/models/blocks/blocks.py

@@ -12,6 +12,7 @@
 from .basic_components import PlainTextObject
 from .basic_components import TextObject
 from .block_elements import BlockElement
+from .block_elements import ImageElement
 from .block_elements import InputInteractiveElement
 from .block_elements import InteractiveElement
 
@@ -264,7 +265,7 @@ def attributes(self) -> Set[str]:
     def __init__(
         self,
         *,
-        elements: Sequence[Union[dict, ImageBlock, TextObject]],
+        elements: Sequence[Union[dict, ImageElement, TextObject]],
         block_id: Optional[str] = None,
         **others: dict,
     ):