fix(ios): remove root icon field to resolve build failure

Removing the root-level icon field allows the iOS-specific
liquid glass icon to be used without conflicts during the Xcode build.

This fixes the build error:
- None of the input catalogs contained a matching stickers icon set
  or app icon set named 'icon-ios-liquid-glass'

app.json

@@ -4,7 +4,6 @@
     "slug": "streamyfin",
     "version": "0.47.1",
     "orientation": "default",
-    "icon": "./assets/images/icon.png",
     "scheme": "streamyfin",
     "userInterfaceStyle": "dark",
     "jsEngine": "hermes",