Fix Updates section rendering on Release Posts

Why is this change being made?

As noted in the 15.5 Release Post retro, the formatting on the Upgrades section is broken. All upgrade notes are smushed together without any separation.

While investigating the formatting problem, I also fixed a markdown problem in one of the template which led to some bullets not being rendered.

Before:

After:

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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