Remove unused variable

synapse/storage/state.py

@@ -378,7 +378,6 @@ class StateStore(SQLBaseStore):
             # We don't use WITH RECURSIVE on sqlite3 as there are distributions
             # that ship with an sqlite3 version that doesn't support it (e.g. wheezy)
             for group in groups:
-                group_tree = [group]
                 next_group = group
 
                 while next_group:
@@ -427,8 +426,6 @@ class StateStore(SQLBaseStore):
                         retcol="prev_state_group",
                         allow_none=True,
                     )
-                    if next_group:
-                        group_tree.append(next_group)
 
         return results