Improving description of timer event specification

[joewarner]

Description

This is a documentation change for the specification of timer events - @camunda/tech-writers

When should this change go live?

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

PR Checklist

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

• I added a DRI, team, or delegate as a reviewer for technical accuracy and grammar/style:
  • Engineering team review
  • Technical writer review via @camunda/tech-writers unless working with an embedded writer.

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[akeller]

Hi @joewarner thanks for your PR! I've reached out to the Modeler team internally to confirm some of the details you have here. Shortly after, I'll assign a tech writer to review.

[philippfromme]

We need someone from the engine team to review this from a technical point of view. I'll let them know.