Update intentional mentions (MSC3952) to depend on exact_event_property_contains (MSC3966). (#15051)

This replaces the specific `is_user_mention` push rule condition
used in MSC3952 with the generic `exact_event_property_contains`
push rule condition from MSC3966.

stubs/synapse/synapse_rust/push.pyi

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Collection, Dict, Mapping, Optional, Sequence, Set, Tuple, Union
+from typing import Any, Collection, Dict, Mapping, Optional, Sequence, Tuple, Union
 
 from synapse.types import JsonDict, JsonValue
 
@@ -58,7 +58,6 @@ class PushRuleEvaluator:
         self,
         flattened_keys: Mapping[str, JsonValue],
         has_mentions: bool,
-        user_mentions: Set[str],
         room_member_count: int,
         sender_power_level: Optional[int],
         notification_power_levels: Mapping[str, int],