Stylelint: Address final two rules (#43296)

* Undisable scss/selector-no-redundant-nesting-selector

* Undisable scss/no-global-function-names

* Add changelogs

* Oops, forgot to @use the modules

* Make $lightness non-unitless

* Another `@use`

* Make more $lightness params un-unitless (or unit-ed)

* Handle deprecated math function

* Two more deprecated math functions

* Undo this calc for now

* Catch a late entry

* Add changelog

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/14762623102

Upstream-Ref: Automattic/jetpack@3f5283f

Author: tbradsha

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 This is an alpha version! The changes listed here are not final.
 
 ### Fixed
+- Linting: Address final rules in WordPress Stylelint config.
 - Linting: Do additional stylesheet cleanup.
 
 ## [0.47.23] - 2025-04-28