Version 0.12.0 ignores remove_alpha_ios setting

### :information_source: Info

Version: `v0.12.0`

### :speech_balloon: Description

I upgraded to 0.12.0, but it broke all my icons suddenly, because remove_alpha_ios option in pubspec.yaml gets ignored now. It worked before with 0.11.0. You can see that in this response:
```
$ flutter pub run flutter_launcher_icons
════════════════════════════════════════════
FLUTTER LAUNCHER ICONS (v0.12.0)
════════════════════════════════════════════

• Creating default icons Android
• Overwriting the default Android launcher icon with a new icon

WARNING: Icons with alpha channel are not allowed in the Apple App Store.
Set "remove_alpha_ios: true" to remove it.

• Overwriting default iOS launcher icon with new icon
Creating Icons for Web...
⚠️Requirements failed for platform Web. Skipped
Creating Icons for Windows...
⚠️Windows config is not provided or windows.generate is false. Skipped...
⚠️Requirements failed for platform Windows. Skipped
Creating Icons for MacOS...
⚠️Requirements failed for platform MacOS. Skipped

✓ Successfully generated launcher icons
```

### :scroll: Pubspec.yaml

```
name: stepslow
description: Simple Music Player for Dancers
# The following line prevents the package from being accidentally published to
# pub.dev using `flutter pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number is used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
# In Windows, build-name is used as the major, minor, and patch parts
# of the product and file versions while build-number is used as the build suffix.
version: 0.2.5+7
homepage: https://www.dvorapa.cz

environment:
sdk: '>=2.12.0 <3.0.0'
flutter: ^3.0.0

# Dependencies specify other packages that your package needs in order to work.
# To automatically upgrade your package dependencies to the latest versions
# consider running `flutter pub upgrade --major-versions`. Alternatively,
# dependencies can be manually updated by changing the version numbers below to
# the latest version available on pub.dev. To see which dependencies have newer
# versions available, run `flutter pub outdated`.
dependencies:
flutter:
sdk: flutter

audioplayers: ^3.0.1
on_audio_query: ^2.6.1
flutter_beep: ^1.0.0
wakelock: '>=0.6.2 <1.0.0'
collection: ^1.17.0
volume_regulator: ^2.1.0
easy_dialogs: ^2.0.0
typicons_flutter: '>=0.5.0 <1.0.0'
shared_preferences: ^2.0.18
yaml: ^3.1.1
ffmpeg_kit_flutter: 5.1.0-LTS
permission_handler: ^10.2.0
path_provider: ^2.0.13
about: ^2.1.1
url_launcher: ^6.1.10
cupertino_icons: ^1.0.5

dev_dependencies:
flutter_launcher_icons: '>=0.12.0 <1.0.0'
pubspec_extract: ^2.0.5
flutter_test:
sdk: flutter
flutter_lints: ^2.0.1

flutter_icons:
image_path: 'assets/icon.png'
android: true
ios: true
remove_alpha_ios: true

flutter:
uses-material-design: true

assets:
- CHANGELOG.md

# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.dev/assets-and-images/#resolution-aware

# For details regarding adding assets from package dependencies, see
# https://flutter.dev/assets-and-images/#from-packages

# To add custom fonts to your application, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts from package dependencies,
# see https://flutter.dev/custom-fonts/#from-packages
```

Reproduce the report with the supplied pubspec.yaml and flutter_launcher_icons v0.12.0, then inspect how remove_alpha_ios is handled and compare that path with v0.11.0. Done means the generated iOS icons no longer retain an alpha channel when remove_alpha_ios: true is set.

Written by the indexing model from the issue text.