Fix fallback value for missing invite power level (#8335)

The spec was recently amended to document that invites actually fall
back to a default of 0, rather than 50 (since this is what Synapse was
doing all along): matrix-org/matrix-spec#1021

src/components/views/right_panel/UserInfo.tsx

@@ -942,7 +942,7 @@ function useRoomPermissions(cli: MatrixClient, room: Room, user: RoomMember): IR
         }
 
         setRoomPermissions({
-            canInvite: me.powerLevel >= (powerLevels.invite ?? 50),
+            canInvite: me.powerLevel >= (powerLevels.invite ?? 0),
             canEdit: modifyLevelMax >= 0,
             modifyLevelMax,
         });

src/components/views/settings/tabs/room/RolesRoomSettingsTab.tsx

@@ -262,7 +262,7 @@ export default class RolesRoomSettingsTab extends React.Component<IProps> {
             },
             "invite": {
                 desc: _t('Invite users'),
-                defaultValue: 50,
+                defaultValue: 0,
             },
             "state_default": {
                 desc: _t('Change settings'),