Update mailtrap.md

[beacampos]

We updated the Mailtrap product itself, and it's no longer a testing tool exclusively. This description is more accurate and still focuses on MODX's users' SMTP based email sending needs.

Description

What does this change, and why is the change needed? The entire description of Mailtrap's function as a tool.

Affected versions

Is the change relevant to 2.x, 3.x, or both? N/A

Relevant issues

Please link to any relevant issues or pull requests.

[Omeryl]

This reads too advertisement focused, to me, it should remain neutral in delivery imho.

[beacampos]

@Omeryl we can go with "Mailtrap is an email delivery platform for(...)" instead of "Mailtrap is a modern email platform(...)", is that ok? The rest doesn't look promotional to me but lmk where else you see it and I can provide other alternatives if needed :)