Fix SVG icons dimensions

[rdwebdesign]

By submitting this pull request, I confirm the following:

• I have read and understood the contributors guide, as well as this entire template.
• I have made only one major change in my proposed changes.
• I have commented my proposed changes within the code.
• I have tested my proposed changes.
• I am willing to help maintain this change if there are issues with it later.
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What does this PR aim to accomplish?:

Fix #2175

How does this PR accomplish the above?:

Use the correct height to size the icons.

What documentation changes (if any) are needed to support this PR?:

none

[yubiuser]

Approving based on code. Maybe someone (@PromoFaux) who actually saw this screen flicker can confirm it's working in reality.

[PromoFaux]

Will check later when I'm home!

[PromoFaux]

Perfecto

[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