Clarify TW RP Item Checklist

Why is this change being made?

Update the TW section of the Release Post Item template. Make it easier for anyone to review every applicable RP feature from a TW PoV.

As discussed in the release-13-0 retro, "feature names can be quite long and almost read like a sentence so it gets unwieldy to capitalize every word of every feature in the intro."

The limit (@cblake and I originally discussed a 5 word limit) is an attempt to facilitate the PMM task for the Release Post.

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 DRI for the page/s being updated isn’t immediately 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.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.

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