enabling no-unused-vars eslint rule (#469)

.eslintrc.js

packages/desktop-client/src/components/MobileWebMessage.js

packages/desktop-client/src/components/SyncRefresh.js

packages/desktop-client/src/components/Titlebar.js

...s/desktop-client/src/components/accounts/MobileAccount.js

.../desktop-client/src/components/accounts/MobileAccounts.js

...sktop-client/src/components/accounts/MobileTransaction.js

...ages/desktop-client/src/components/budget/MobileBudget.js

...desktop-client/src/components/budget/MobileBudgetTable.js

...top-client/src/components/reports/graphs/NetWorthGraph.js

packages/desktop-client/src/components/settings/UI.js

packages/loot-core/src/platform/exceptions/index.web.js

packages/loot-design/src/components/common.js

packages/loot-design/src/components/sidebar.js

packages/loot-design/src/setupTests.js