Repository: flutter
Issue: [BUG]Unnecessary additional parameters generated for mismatched placeholders
Labels: framework,a: internationalization,has reproducible steps,P2,found in release: 3.7,found in release: 3.8,team-framework,triaged-framework

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## Steps to Reproduce

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- Setup localization referencing [flutter documentation](https://docs.flutter.dev/development/accessibility-and-localization/internationalization)
- Define a simple translation with required placeholders not matching placeholder meta data reference (when cases are different)
- Generate app-localization files running `flutter gen-l10n` in the project's terminal

**Expected results:** Required placeholders should be the generated parameters for app-localization

**Actual results:** More than the required placeholders are part of the required parameters for the generated app-localization file when the placeholders don't match their placeholders-meta counterparts

<details>
<summary>Code sample</summary>

Simply put, a translation file object requiring placeholder(s) to be parsed with non-matching placeholder(s) in the object’s placeholders-meta object will result to generating more-than-specified parameters for a translation object key.

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Requires `convertFrom` and `convertTo` placeholders which is not matching the meta-placeholders `convertfrom` and `convertto` keys due to case differences
```arb
{
	"@@locale": "en",
	"convert_before_withdraw_again": "* For withdrawing your {convertFrom} you first need to convert it back to {convertTo}",
	"@convert_before_withdraw_again": {
		"type": "text",
		"placeholders": {
			"convertfrom": {},
			"convertto": {}
		}
	}
}
```

Will result to generating (observe the `convert_before_withdraw_again` parameter casing)
```dart
class AppLocalizationsEn extends AppLocalizations {
	@override
 	 String convert_before_withdraw_again(Object convertFrom, Object convertTo, Object convertfrom, Object convertto) {
    		return '* For withdrawing your $convertFrom you first need to convert it back to $convertTo';
  	}
}
```

</details>

<details>
  <summary>Logs</summary>

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```
```

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```
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
 Flutter (Channel stable, 3.7.1, on macOS 13.1 22C65 darwin-arm64, locale en-EE)
    • Flutter version 3.7.1 on channel stable at /Users/christian.onwe/source/flutter
    ! Warning: `dart` on your path resolves to
      /opt/homebrew/Cellar/dart/2.19.0/libexec/bin/dart, which is not inside your
      current Flutter SDK checkout at /Users/christian.onwe/source/flutter. Consider
      adding /Users/christian.onwe/source/flutter/bin to the front of your path.
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 7048ed95a5 (3 days ago), 2023-02-01 09:07:31 -0800
    • Engine revision 800594f1f4
    • Dart version 2.19.1
    • DevTools version 2.20.1
    • If those were intentional, you can disregard the above warnings; however it is
      recommended to use "git" directly to perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
    • Android SDK at /Users/christian.onwe/Library/Android/sdk
    • Platform android-33, build-tools 33.0.0
    • Java binary at: /Applications/Android
      Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14C18
    • CocoaPods version 1.11.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2021.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)

[✓] VS Code (version 1.75.0)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.58.0

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-arm64   • macOS 13.1 22C65 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 109.0.5414.119

[✓] HTTP Host Availability
    • All required HTTP hosts are available

! Doctor found issues in 1 category.
```

</details>


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