Improve product stages and groups page discoverability

Why is this change being made?

Related to gitlab-org/quality/contributor-success/team#64, I would like to make it easier to reach the page where all the stages, groups and categories of the product are listed.

This MR does not change much but by changing the title of the link on the homepage and the product page will, hopefully, improve the discoverability of said page 🙂

Moreover, that was maybe the only link title that did not match the title of the page it linked to 🙂

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • 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
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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