Remove synapse.types.Collection (#9856)

This is no longer required, since we have dropped support for Python 3.5.

synapse/handlers/sync.py

@@ -14,7 +14,17 @@
 # limitations under the License.
 import itertools
 import logging
-from typing import TYPE_CHECKING, Any, Dict, FrozenSet, List, Optional, Set, Tuple
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Collection,
+    Dict,
+    FrozenSet,
+    List,
+    Optional,
+    Set,
+    Tuple,
+)
 
 import attr
 from prometheus_client import Counter
@@ -28,7 +38,6 @@ from synapse.push.clientformat import format_push_rules_for_user
 from synapse.storage.roommember import MemberSummary
 from synapse.storage.state import StateFilter
 from synapse.types import (
-    Collection,
     JsonDict,
     MutableStateMap,
     Requester,