Change Mentions base model from AgentsModel to Entity (#63)

* port test case from botframework for turn-context

* fix  model to derive from  instead of

* fix branches

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Co-authored-by: = <=>
Co-authored-by: Axel Suárez <axsuarez@microsoft.com>

Author: kylerohnmsft

libraries/Core/microsoft-agents-core/microsoft/agents/core/models/mention.py

@@ -1,9 +1,9 @@
 from .channel_account import ChannelAccount
-from .agents_model import AgentsModel
+from .entity import Entity
 from ._type_aliases import NonEmptyString
 
 
-class Mention(AgentsModel):
+class Mention(Entity):
     """Mention information (entity type: "mention").
 
     :param mentioned: The mentioned user