Update source/handbook/sales/onboarding/sales-learning-path/index.html.md

Why is this change being made?

Suggestion from Michelle Hodges to add “Ten Reasons Not to Start with GitLab Starter" to https://about.gitlab.com/handbook/sales/onboarding/sales-learning-path/#6-our-portfolio.

Recommendation:

1. As a short-term solution, add this How to Upgrade Your Customer to a Higher Tier video to SQS learning path and channel accreditations
2. Replace with https://gitlab.com/gitlab-com/sales-team/sales-enablement-videocast-series/-/issues/40 when this is prioritized and delivered
3. Augment with https://gitlab.com/gitlab-com/sales-team/field-operations/enablement/issues/115 once content is added to the Handbook

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the change relates to any part of the project other than updates to content and/or data files (e.g. team.yml) please make sure to ping @gl-static-site-editor in a comment for a review and merge.
  • If the DRI for the page/s being updated isn't immediate clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies

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