Merge pull request #749 from textpattern/dependabot/npm_and_yarn/postcss-8.5.9

Bump postcss from 8.5.8 to 8.5.9

Author: petecooper

package.json

@@ -25,7 +25,7 @@
     "grunt-stylelint": "0.20.1",
     "grunt-terser": "2.0.0",
     "load-grunt-tasks": "5.1.0",
-    "postcss": "8.5.8",
+    "postcss": "8.5.9",
     "sass": "1.99.0",
     "stylelint": "17.6.0",
     "stylelint-config-standard-scss": "17.0.0",