Microbatch illustrations incorrectly imply --event-time-end is inclusive

### Contributions

- [x] I have read the contribution docs, and understand what's expected of me.

### Link to the page on docs.getdbt.com requiring updates

https://docs.getdbt.com/docs/build/incremental-microbatch#backfills

### What part(s) of the page would you like to see updated?

Diagram depicting the valid range for "Configure a lookback to reprocess additional batches during standard incremental runs" incorrectly indicates that 2024-05-13 will be included when, in practice, --event-time-end is **exclusive**.

### Additional information

_No response_

Open the linked incremental microbatch documentation and read the Backfills section, focusing on the diagram for configuring a lookback during standard incremental runs. Update the diagram so it represents --event-time-end as exclusive and does not show 2024-05-13 as included; verify the rendered page matches that behavior.

Written by the indexing model from the issue text.