Fix web build by removing app icon settings (#6784)

src/screens/Settings/AppIconSettings.web.tsx

···
+export function AppIconSettingsScreen() {
+  throw new Error('Not supported on web')
+}

src/screens/Settings/AppearanceSettings.tsx

···
 
 import {DISCOVER_DEBUG_DIDS} from '#/lib/constants'
 import {CommonNavigatorParams, NativeStackScreenProps} from '#/lib/routes/types'
+import {isNative} from '#/platform/detection'
 import {useSession} from '#/state/session'
 import {useSetThemePrefs, useThemePrefs} from '#/state/shell'
 import {Logo} from '#/view/icons/Logo'
···
                 onChange={onChangeFontScale}
               />
 
-              {DISCOVER_DEBUG_DIDS[currentAccount?.did ?? ''] && (
+              {isNative && DISCOVER_DEBUG_DIDS[currentAccount?.did ?? ''] && (
                 <>
                   <SettingsList.Divider />