feat: add tag name to GroupSet

Author: jorwoods

tableauserverclient/models/groupset_item.py

@@ -7,6 +7,8 @@
 
 
 class GroupSetItem:
+    tag_name: str = "groupSet"
+
     def __init__(self, name: Optional[str] = None) -> None:
         self.name = name
         self.id: Optional[str] = None