Icon change is not working for MacOS[BUG]

### :information_source: Info

Version: `e.g. v0.7.5`
flutter_launcher_icons: ^0.13.1

### :speech_balloon: Description

I changed the icon file and ran the commands below:
```
flutter pub get
flutter pub run flutter_launcher_icons
```
After I ran the app `flutter run -d MacOS` but the old icon is still in use. I even renamed the icon file to `old-icon` and the old icon is still showing. However, in the terminal I got the following error:
```
══╡ EXCEPTION CAUGHT BY IMAGE RESOURCE SERVICE ╞════════════════════════════════════════════════════
The following assertion was thrown resolving an image codec:
Unable to load asset: "assets/images/icon.png".
Exception: Asset not found

When the exception was thrown, this was the stack:
#0 PlatformAssetBundle.loadBuffer (package:flutter/src/services/asset_bundle.dart:365:7)

#1 AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:754:16)

#2 MultiFrameImageStreamCompleter._handleCodecReady (package:flutter/src/painting/image_stream.dart:1005:3)

Image provider: AssetImage(bundle: null, name: "assets/images/icon.png")
Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#05844(), name: "assets/images/icon.png",
scale: 1.0)
════════════════════════════════════════════════════════════════════════════════════════════════════
```

### :scroll: Pubspec.yaml

```
flutter_launcher_icons:
android: "launcher_icon"
ios: true
image_path: "assets/images/icon-new.png"
min_sdk_android: 21 # android min sdk min:16, default 21
web:
generate: true
image_path: "assets/images/icon-new.png"
background_color: "#hexcode"
theme_color: "#hexcode"
windows:
generate: true
image_path: "assets/images/icon-new.png"
icon_size: 48 # min:48, max:256, default: 48
macos:
generate: true
image_path: "assets/images/icon-new.png"
```

We ask that you include your pubspec.yaml file as a common problem we have seen has been the pubspec.yaml file being incorrect

Reproduce the report with flutter pub get, flutter pub run flutter_launcher_icons, and flutter run -d MacOS using the shown macos configuration. Check whether the generated macOS icon reflects assets/images/icon-new.png and determine whether the reported old icon or missing asset error remains.

Written by the indexing model from the issue text.