update gateway service protobuf references

[christinaausley]

Description

Closes #3367.

Updates protobuf references based on https://github.com/camunda/camunda/blob/86828ff3fd3caef48b3229c1f717466b35c955eb/gateway-protocol/src/main/proto/gateway.proto

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).

To backport upon approval

• My changes require an Engineering review, and I've assigned the Engineering DRI or delegate.
• My changes require a technical writer review, and I've assigned @camunda/tech-writers as a reviewer.

[github-actions]

👋 🤖 ✅ Looks like the changes were ported across versions, nice job! 🎉

You can read more about the versioning within our docs in our documentation guidelines.

[akeller]

I noticed these reference keys were removed. Is there more context here? Is this not something we want to recommend, or is there an alternative now?

[christinaausley]

These were removed in the protobuf, but I'll leave it up to @korthout if we want to keep this in the docs?

[christinaausley]

CC @megglos

[megglos]

will check on the background, but generally if they are gone from the protobuf, we should remove them from the docs too

[christinaausley]

@akeller As @megglos is out on parental leave for about a month, I think we can go ahead and merge this. If he returns and decides to add the reference keys we can certainly pop them back in!