Refactor: src/screens/UserPortal/Campaigns from Jest to Vitest

[VanshikaSabharwal]

Is your feature request related to a problem? Please describe.
This file is currently tested using Jest. As part of our migration to Vitest, we need to refactor this file's test cases to align with Vitest's syntax and features.

Acceptance Criteria

1. Replace Jest-specific functions and mocks with Vitest equivalents
2. Ensure all tests in src/screens/UserPortal/Campaigns pass after migration using npm run test:vitest
3. Maintain the test coverage for the file as 100% after migration
4. Upload a video or photo for this specific file coverage is 100% in the PR description

Additional context

• Refer to the merged PR for the base Vitest configuration:
  https://github.com/PalisadoesFoundation/talawa-admin/pull/2457/files#diff-9a5a35cf8d7f02b2bba90905714b762560579c4789e9eb4cebb4607980aa3d93
• Vitest documentation:
  https://vitest.dev/

Potential internship candidates

Please read this if you are planning to apply for a Palisadoes Foundation internship

• Student Internship Programs talawa#359

[rafidoth]

@palisadoes Can you assign this to me, I want to work on this

[palisadoes]

Unassigning due to inactivity and/or no submitted PR. Others need to get a chance. Please let us know whether you want to be reassigned before someone else requests assignment or select another issue.

[rafidoth]

@palisadoes you merged commit 11ece4a and also the issue got closed as completed. Can you explain what to do now? I'll do that.