Repository: flutter
Issue: update_dart_sdk.ps1 not digitally signed on Windows
Labels: tool,platform-windows,t: flutter doctor,P2,team-tool,triaged-tool

### Is there an existing issue for this?

- [X] I have searched the [existing issues](https://github.com/flutter/flutter/issues)
- [X] I have read the [guide to filing a bug](https://flutter.dev/docs/resources/bug-reports)

### Steps to reproduce

1. Change the script execution policy using Group Policy (requires Windows Pro)

![image](https://github.com/flutter/flutter/assets/10885603/b381fc6c-92cd-4fde-b988-08db49383820)

2. Execute any flutter commands (e.g., `flutter doctor`)

The previous issues were closed due to inactivity:

1. #50934
2. #39692


### Expected results

The PowerShell script should be signed to work on Windows machines with policies restricting executing signed scripts only

### Actual results

The script `flutter\bin\internal\update_dart_sdk.ps1` is not digitally signed. Upon executing Flutter commands like `flutter doctor` or `flutter upgrade` the error would show

### Code sample

<details><summary>Code sample</summary>

```bash
flutter doctor
```

</details>


### Screenshots or Video

<details>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details><summary>Logs</summary>

```console
& : File C:\flutter\bin\internal\update_dart_sdk.ps1 cannot be loaded. The file
C:\flutter\bin\internal\update_dart_sdk.ps1 is not digitally signed. You cannot run this script on the
current system. For more information about running scripts and setting execution policy, see about_Execution_Policies
at https:/go.microsoft.com/fwlink/?LinkID=135170.
At line:1 char:81
+ ... sdk.ps1'; & 'C:\flutter\bin\internal\update_dart_sdk.ps1' ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : SecurityError: (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess
```

</details>


### Flutter Doctor output

<details><summary>Doctor output</summary>

```console
> flutter doctor
Checking Dart SDK version...
Downloading Dart SDK from Flutter engine b20183e04096094bcc37d9cde2a4b96f5cc684cf...
& : File C:\flutter\bin\internal\update_dart_sdk.ps1 cannot be loaded. The file
C:\flutter\bin\internal\update_dart_sdk.ps1 is not digitally signed. You cannot run this script on the
current system. For more information about running scripts and setting execution policy, see about_Execution_Policies
at https:/go.microsoft.com/fwlink/?LinkID=135170.
At line:1 char:81
+ ... sdk.ps1'; & 'C:\flutter\bin\internal\update_dart_sdk.ps1' ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : SecurityError: (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess
Building flutter tool...
Running pub upgrade...
Resolving dependencies... (3.0s)
Got dependencies.
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.13.2, on Microsoft Windows [Version 10.0.22621.2134], locale en-US)
[✓] Windows Version (Installed version of Windows is version 10 or higher)
[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.2)
[✓] Chrome - develop for the web
[✓] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.7.2)
[✓] Android Studio (version 2022.1)
[✓] IntelliJ IDEA Ultimate Edition (version 2023.1)
[✓] VS Code (version 1.81.1)
[✓] Connected device (1 available)
[✓] Network resources

• No issues found!
```

</details>