Shorten timeline events headings

What does this MR do?

Shorten timeline events headings.

For a non-native speaker of English, "timeline event" and"event timeline" may be difficult to distinguish. This makes the headings clear what the object of the action is.

Before	After
View the event timeline	View the timeline
Create a timeline event	Create an event
Delete a timeline event	Delete an event

Related issues

Fixes Follow-up from "Move timeline events doc to a n... (#372627 - closed)

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