Update dependency postcss to v8.4.26

Author: renovate[bot]

package-lock.json

@@ -23,7 +23,7 @@
     "css-loader": "6.8.1",
     "html-webpack-plugin": "5.5.3",
     "mini-css-extract-plugin": "2.7.6",
-    "postcss": "8.4.25",
+    "postcss": "8.4.26",
     "postcss-loader": "7.3.3",
     "sass": "1.63.6",
     "sass-loader": "13.3.2",