Clarify when & how to get an Enterprise License to contribute

What does this MR do and why?

Explaining what "versions" we have does not seem appropriate in the "how to contribute". I always found it confusing to talk about licenses when in reality, you want to work on Features in a paid tier. I understand this is due to the license model, but those complexities can be explained elsewhere. The MR tries to make this simpler and more to the point of what a contributor (in my opinion) wants to achieve.

It also fixes 2 URLS since the rename of community-relations to developer-relations

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