Add @web-stories-wp prefix to karma packages name

[mohdsayed]

Context

Add @web-stories-wp prefix to karma packages name.

Summary

Relevant Technical Choices

To-do

User-facing changes

Testing Instructions

QA

• This is a non-user-facing change and requires no QA

This PR can be tested by following these steps:

UAT

• UAT should use the same steps as above.

This PR can be tested by following these steps:

Reviews

Does this PR have a security-related impact?

Does this PR change what data or activity we track or use?

Does this PR have a legal-related impact?

Checklist

• This PR addresses an existing issue and I have linked this PR to it in ZenHub
• I have tested this code to the best of my abilities
• I have verified accessibility to the best of my abilities (docs)
• I have verified i18n and l10n (translation, right-to-left layout) to the best of my abilities
• This PR contains automated tests (unit, integration, and/or e2e) to verify the code works as intended (docs)
• I have added documentation where necessary
• I have added a matching Type: XYZ label to the PR

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Related: #8537 (comment)