3.8-ify one last thing

matrix_appservice_kakaotalk/kt/types/api/struct/friends/friend_search_struct.py

@@ -13,7 +13,7 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
-from typing import Optional
+from typing import List, Optional
 
 from attr import dataclass
 
@@ -25,7 +25,7 @@ from .friend_struct import FriendStruct
 @dataclass
 class FriendSearchUserListStruct(SerializableAttrs):
     count: int
-    list: list[FriendStruct]
+    list: List[FriendStruct]
 
 
 @dataclass(kw_only=True)
@@ -33,7 +33,7 @@ class FriendSearchStruct(SerializableAttrs):
     query: str
     user: Optional[FriendSearchUserListStruct] = None
     plus: Optional[FriendSearchUserListStruct] = None
-    categories: list[str]
+    categories: List[str]
     total_counts: int