chore(package): update autoprefixer to version 9.4.3

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "url": "https://github.com/philwareham/textpattern-classic-admin-theme/issues"
   },
   "devDependencies": {
-    "autoprefixer": "9.4.2",
+    "autoprefixer": "9.4.3",
     "cssnano": "4.1.7",
     "dart-sass": "1.15.2",
     "fibers": "3.1.1",