Fix Typos and Broken Links in Competencies Page

Why is this change being made?

I noticed a few broken links and typos while reading through this page.

wil->will

The link to GitLab administration is broken since that is part of the GitLab docs and not the handbook.

1. [GitLab administration](/ee/administration/) -> 1. [GitLab administration](https://docs.gitlab.com/ee/administration/)

The link to the iteration page gives a 404

1. [Iteration](/handbook/iteration) -> 1. [Iteration](/handbook/values/#iteration)

Author Checklist

• Provided a concise title for the MR
• [s] 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

For help with failing pipelines reach out in #mr-buddies in Slack