Update doc/api/jobs.md

What does this MR do?

Improves Jobs API documentation to include information regarding paginated data.

Related issues

I had this issue myself and spent hours debugging my script only to realize the API does not return all jobs and is in fact paginated. Following issues seem to be relevant as well, which hints that this may be a common misunderstanding:

• https://stackoverflow.com/questions/64394016/gitlab-api-pipeline-not-returning-all-jobs
• https://stackoverflow.com/questions/63793106/cannot-fetch-all-jobs-from-gitlab-with-curl
• https://stackoverflow.com/questions/29845852/gitlab-api-get-group-list-only-20-groups-not-all
• #206922 (closed)

Related to #22976

Review checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
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  • Ensure the appropriate labels are added to this MR.
  • If relevant to this MR, ensure content topic type principles are in use, including:
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    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
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• Ensure a release milestone is set.