Merge pull request #785 from textpattern/dependabot/npm_and_yarn/postcss-8.5.21

Bump postcss from 8.5.19 to 8.5.21

Author: petecooper

package.json

@@ -25,7 +25,7 @@
     "grunt-stylelint": "0.21.0",
     "grunt-terser": "2.0.0",
     "load-grunt-tasks": "5.1.0",
-    "postcss": "8.5.19",
+    "postcss": "8.5.21",
     "sass": "1.101.0",
     "stylelint": "17.14.0",
     "stylelint-config-standard-scss": "17.0.0",