Replace job with group in frontend components to be consistent with backend

What does this MR do?

Uses the term group in the frontend for multiple CI jobs of a stage to be consistent with the backend.

What are the relevant issue numbers?

part of https://gitlab.com/gitlab-org/gitlab-ce/issues/52135

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides