chore(stylelint): re-enable standard color and specificity rules (#945)

Author: gildesmarais

frontend/stylelint.config.mjs

@@ -3,12 +3,6 @@ export default {
   extends: ["stylelint-config-standard"],
   ignoreFiles: ["dist/**/*.css", "node_modules/**/*.css"],
   rules: {
-    // Keep this PR scoped to toolchain migration; don't force legacy CSS rewrites yet.
-    "alpha-value-notation": null,
-    "color-function-alias-notation": null,
-    "color-function-notation": null,
-    "media-feature-range-notation": null,
-    "no-descending-specificity": null,
     "selector-class-pattern": [
       "^[a-z][a-z0-9]*(?:-[a-z0-9]+)*(?:__(?:[a-z0-9]+(?:-[a-z0-9]+)*))?(?:--(?:[a-z0-9]+(?:-[a-z0-9]+)*))?$",
       {