iPhone app switcher uses default icons

### :information_source: Info

v0.14.4

### :speech_balloon: Description

When generating some iOS icons are left untouched:
- `Icon-App-20x20@1x.png`
- `Icon-App-29x29@1x.png`
- `Icon-App-40x40@1x.png`
- `Icon-App-76x76@1x.png`

because of that flutter icon is still used in app switcher (see screenshot below):

### :scroll: Pubspec.yaml

```yaml
flutter_launcher_icons:
android: true
ios: true
remove_alpha_ios: true
image_path: "assets/icons/icon.png"
image_path_ios: "assets/icons/ios-light.png"
image_path_ios_dark_transparent: "assets/icons/ios-dark-transparent.png"
image_path_ios_tinted_grayscale: "assets/icons/ios-tinted.png"
adaptive_icon_background: "#ffffff"
adaptive_icon_foreground: "assets/icons/adaptive-icon.png"
adaptive_icon_monochrome: "assets/icons/adaptive-icon.png"
adaptive_icon_foreground_inset: 0
web:
generate: true
image_path: "assets/icons/favicon.png"
```

Reproduce the issue with the v0.14.4 configuration shown in the report and inspect the generated iOS assets, especially Icon-App-20x20@1x.png, Icon-App-29x29@1x.png, Icon-App-40x40@1x.png, and Icon-App-76x76@1x.png. Compare them with the configured iOS source images and verify that all required icons are regenerated so the app switcher no longer shows the default Flutter icon.

Written by the indexing model from the issue text.