Update dependency postcss to v8.5.9

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
postcss (source)	8.5.3 → 8.5.9

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Release Notes

postcss/postcss (postcss)

v8.5.9

Compare Source

• Speed up source map encoding paring in case of the error.

v8.5.8

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• Fixed Processor#version.

v8.5.7

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• Improved source map annotation cleaning performance (by CodeAnt AI).

v8.5.6

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• Fixed ContainerWithChildren type discriminating (by @​Goodwine).

v8.5.5

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• Fixed package.json→exports compatibility with some tools (by @​JounQin).

v8.5.4

Compare Source

• Fixed Parcel compatibility issue (by @​git-sumitchaudhary).

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