Standardize styling of "Planet" in manual overview

[RyanS4]

Please verify the following:

• This issue is related to the Virtual Interns First Steps document or Planet User Manual.
• You have searched for relevant keywords in recent open and closed issues to avoid duplicates.

URL to the MDwiki page containing the problem

https://open-learning-exchange.github.io/#!pages/manual/planet/overview.md

Problem

Currently, "Planet" is being written in different styles throughout the doc (ex. some instances of PLANET are present).

Screenshots (when necessary)

No response

Proposed solution(s)

All instances of PLANET on the overview page of the Planet Manual should be changes to "PLANET" to better match the consistency found throughout the rest of the wiki.