Replace MatrixClient.isCryptoEnabled by MatrixClient.getCrypto (#140)

* Replace `MatrixClient.isCryptoEnabled` by `MatrixClient.getCrypto`

* Cast `cryptoEnabled` as `boolean`

* Fix `MatrixChat-test`

(cherry picked from commit 950ab1940bfcea9443f03284f9175d319c13a44c)

test/unit-tests/components/views/dialogs/security/CreateSecretStorageDialog-test.tsx

@@ -134,8 +134,6 @@ describe("CreateSecretStorageDialog", () => {
         });
 
         it("calls bootstrapSecretStorage once keys are restored if the backup is now trusted", async () => {
-            mockClient.isCryptoEnabled.mockReturnValue(true);
-
             const result = renderComponent();
             await result.findByText(/Enter your account password to confirm the upgrade/);
             expect(result.container).toMatchSnapshot();