fix: add entry for brevo to publicApi definition mappers

[gabeleonpma]

trafficstars

What

• Currently, one cannot use the API https://reference.airbyte.com/reference/createsource for Brevo. This is because the mapping from the name to the source definition ID is not present.
• This results in requests in responses of type 400, saying that the value brevo of the sourceType could not be found.

How

• The mapping for the sourceType brevo is mapped to its corresponding source definition ID.

Can this PR be safely reverted and rolled back?

• [x] YES 💚
• [ ] NO ❌