Update dependency gulp-autoprefixer to v8

Author: renovate-bot

package-lock.json

@@ -46,7 +46,7 @@
     "clipboard": "2.0.6",
     "datatables.net": "1.10.22",
     "gulp": "4.0.2",
-    "gulp-autoprefixer": "7.0.1",
+    "gulp-autoprefixer": "8.0.0",
     "gulp-babel": "8.0.0",
     "gulp-bump": "3.2.0",
     "gulp-clean": "0.4.0",