Update Rust crate color_quant to v2

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
color_quant	dependencies	major	1.1.0 → 2.0.0

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Release Notes

image-rs/color_quant (color_quant)

v2.0.0

• Add no_std support using core and alloc only, and raise the MSRV from Rust 1.34.2 to 1.36.0 (#​24)
• Add NeuQuant::color_map_alpha for retrieving the palette alpha channel, useful for PNG tRNS chunks (#​23)
• Fix search_netindex so palette index 0 is checked and both search directions are handled correctly (#​16)
• Fix a sampling prime typo by changing 478 to 487 (#​14)
• Forbid unsafe code in the crate (#​22)
• Improve and specialize internal math operations used by the quantizer, and document their provenance (#​24)

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