Scale axes to integer

[yubiuser]

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What does this PR aim to accomplish?:

Prevents the timeline charts at the dashboard to scale the y-axis with floating-point numbers.

How does this PR accomplish the above?:

Use precision from https://www.chartjs.org/docs/2.9.4/axes/cartesian/linear.html

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-16-web-v5-13-and-core-v5-11-1-released/56384/1