fix(account-list-menu): set empty className to string instead of boolean

Fix browser console error:
Warning: Failed prop type: Invalid prop `className` of type `boolean` supplied to `TextFieldSearch`, expected `string`.
    in TextFieldSearch (at account-list-menu.tsx:396)
    in AccountListMenu (at routes.component.js:916)
    in div (at routes.component.js:891)
    in Routes (created by Connect(Routes))
    in Connect(Routes) (created by Context.Consumer)
    in withRouter(Connect(Routes)) (at pages/index.js:54)
    in MetamaskNotificationsProvider (at pages/index.js:53)
    in CurrencyRateProvider (at pages/index.js:52)
    in LegacyI18nProvider (at pages/index.js:51)
    in I18nProvider (at pages/index.js:50)
    in LegacyMetaMetricsProvider (at pages/index.js:49)
    in MetaMetricsProvider (at pages/index.js:48)
    in RenderedRoute (created by Routes)
    in Routes (created by CompatRouter)
    in Router (created by CompatRouter)
    in CompatRouter (at pages/index.js:47)
    in Router (created by HashRouter)
    in HashRouter (at pages/index.js:46)
    in Provider (at pages/index.js:45)
    in Index (at ui/index.js:214)
Warning: Failed prop type: Invalid prop `endAccessory` supplied to `TextFieldSearch`, expected a ReactNode.
    in TextFieldSearch (at account-list-menu.tsx:396)
    in AccountListMenu (at routes.component.js:916)
    in div (at routes.component.js:891)
    in Routes (created by Connect(Routes))
    in Connect(Routes) (created by Context.Consumer)
    in withRouter(Connect(Routes)) (at pages/index.js:54)
    in MetamaskNotificationsProvider (at pages/index.js:53)
    in CurrencyRateProvider (at pages/index.js:52)
    in LegacyI18nProvider (at pages/index.js:51)
    in I18nProvider (at pages/index.js:50)
    in LegacyMetaMetricsProvider (at pages/index.js:49)
    in MetaMetricsProvider (at pages/index.js:48)
    in RenderedRoute (created by Routes)
    in Routes (created by CompatRouter)
    in Router (created by CompatRouter)
    in CompatRouter (at pages/index.js:47)
    in Router (created by HashRouter)
    in HashRouter (at pages/index.js:46)
    in Provider (at pages/index.js:45)
    in Index (at ui/index.js:214)

ui/components/multichain/account-list-menu/account-list-menu.tsx

@@ -583,8 +583,8 @@ export const AccountListMenu = ({
                   }}
                   inputProps={{ autoFocus: true }}
                   // TODO: These props are required in the TextFieldSearch component. These should be optional
-                  endAccessory
-                  className
+                  endAccessory={null}
+                  className=''
                 />
               </Box>
             ) : null}