BD-3477 Remove "send_id" for several message events

[rachel-feinberg]

Summary

My PR removes send_id for a few SMS message engagement events

Related PRs, issues, or features (optional)

BD-3477

Feature release date (optional)

• N/A

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[jeffreystutz]

These fields were all empty historically, correct? I have no objection to us making the code change, but for cloud storage connectors we'll need to pre-announce the change, and we should keep the field in the docs until then. We can update the string to say that it's deprecated so that there are no questions about why it's empty/missing.

So I'd say let's do the following:

1. Update the docs to say the field is deprecated
2. Release the change to partners, since there shouldn't be any change anyway
3. Get new PRs ready for making the code change for cloud storage and removing the field from the docs. Hold off on releasing until our next release, which will include communications ahead of time.

Does that work for everyone?