chore(deps): update dependency cssnano to ~5.1.15

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
cssnano	~5.1.14 -> ~5.1.15

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Release Notes

cssnano/cssnano

### [`v5.1.15`](https://togithub.com/cssnano/cssnano/releases/tag/cssnano%405.1.15): v5.1.15 [Compare Source](https://togithub.com/cssnano/cssnano/compare/cssnano@5.1.14...cssnano@5.1.15) ##### Bug Fixes - fix(postcsss-reduce-initial): fix mask-repeat conversion - fix(postcss-colormin): don't minify colors in src declarations - fix(postcss-merge-rules): do not merge conflicting flex and border properties

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Configuration

📅 Schedule: Branch creation - "before 5am on saturday" in timezone Asia/Jakarta, Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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