Upgrade eslint-plugin-matrix-org to 1.2.1

This upgrade came with a number of new lints that needed to be fixed across the code base. Primarily: explicit return types on functions, and explicit visibility modifiers on class members.

src/UserMenuContainer.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { useCallback, useState } from "react";
+import { FC, useCallback, useState } from "react";
 import { useHistory, useLocation } from "react-router-dom";
 
 import { useClientLegacy } from "./ClientContext";
@@ -26,7 +26,7 @@ interface Props {
   preventNavigation?: boolean;
 }
 
-export function UserMenuContainer({ preventNavigation = false }: Props) {
+export const UserMenuContainer: FC<Props> = ({ preventNavigation = false }) => {
   const location = useLocation();
   const history = useHistory();
   const { client, logout, authenticated, passwordlessUser } = useClientLegacy();
@@ -83,4 +83,4 @@ export function UserMenuContainer({ preventNavigation = false }: Props) {
       )}
     </>
   );
-}
+};