Second batch: remove deprecated calls on `MatrixClient` (#28227)

* Replace `MatrixClient.forceDiscardSession` call by `MatrixClient.CryptoApi.forceDiscardSession`

* Remove `MatrixClient.scheduleAllGroupSessionsForBackup` mock

src/SlashCommands.tsx

@@ -727,7 +727,7 @@ export const Commands = [
         isEnabled: (cli) => !isCurrentLocalRoom(cli),
         runFn: function (cli, roomId) {
             try {
-                cli.forceDiscardSession(roomId);
+                cli.getCrypto()?.forceDiscardSession(roomId);
             } catch (e) {
                 return reject(e instanceof Error ? e.message : e);
             }

test/test-utils/test-utils.ts

@@ -166,7 +166,6 @@ export function createTestClient(): MatrixClient {
             });
         }),
         mxcUrlToHttp: jest.fn().mockImplementation((mxc: string) => `http://this.is.a.url/${mxc.substring(6)}`),
-        scheduleAllGroupSessionsForBackup: jest.fn().mockResolvedValue(undefined),
         setAccountData: jest.fn(),
         setRoomAccountData: jest.fn(),
         setRoomTopic: jest.fn(),