fix(dev-env): demo code is displayed as [demo-image]

[sjinks]

Description

There was an inconsistency in how the demo code was displayed in vip dev-env info --extended.
For example, if we invoke vip dev-env create -u demo < /dev/null, both MU Plugins and the Application Code will use a demo image, but it will be displayed differently:

$ vip dev-env info --extended | grep -E 'PLUGINS|CODE'
 MU PLUGINS        demo                                                                                               
 APP CODE          [demo-image]                                                                                       

This PR makes this consistent: [demo-image]

Pull request checklist

• Update SETUP.md with any new environmental variables.
• Update the documentation.
• Manually test the relevant changes.
• Follow the pull request checklist
• Add/update automated tests as needed.

New release checklist

• Automated tests pass.
• The Preparing for release checklist is completed.

Steps to Test

See above.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details

Scanned Manifest Files

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud