replace deprecated util with core

[m-aboelenein]

🔘 PR Type

What kind of change does this PR introduce?

• Code style update (formatting, local variables)

📜 Background

Using the newly exported getAppIconFromWebManifest from core

🖼 Screenshot / 📹 Video

✅ Review checklist

Please ensure the following are true before merging:

• Code Style is consistent with the project guidelines.
• Code is readable and well-commented.
• No unnecessary or debugging code has been added.
• Security considerations have been taken into account.
• The change has been manually tested and works as expected.
• Breaking changes and their impacts have been considered and documented.
• Code does not introduce new technical debt or issues.

[github-actions]

Test with build here: https://github.com/secretkeylabs/xverse-web-extension/actions/runs/7752658884

[teebszet]

@DuskaT021 I'll test this one. it's a minor change