Remove unknowns & defaults should also works within 𝚜𝚝𝚢𝚕𝚎 attribute

[KrasnayaPloshchad]

Describe the bug
Although SVGO have an removeUnknownsAndDefaults plugin, it doesn’t works with CSS properties in style attribute, instead, it must works with convertStyleToAttrs.js

To Reproduce
Steps to reproduce the behavior:

1. Download https://upload.wikimedia.org/wikipedia/commons/archive/3/30/20200701055512%21PatriarchsCross.svg
2. Optimize with SVGO
3. Enable removeUnknownsAndDefaults.js
4. See error

Expected behavior
This should be able to clean up CSS styles as well, which would be more useful for SVGs created by major SVG editors.

Screenshots
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Desktop (please complete the following information):

• SVGO Version 3.0.0 (through SVGOMG)
• NodeJs Version N/A
• OS: Android

Additional context
Add any other context about the problem here.