remove unnecessary charset at-rule from CSS

webpack.config.js

@@ -11,7 +11,6 @@ import TerserPlugin from "terser-webpack-plugin";
 import autoprefixer from "autoprefixer";
 import postcssSvgo from "postcss-svgo";
 import postcssFocus from "postcss-focus";
-import postcssNormalizeCharset from "postcss-normalize-charset";
 
 // https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c#what-do-i-use-instead-of-__dirname-and-__filename
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
@@ -132,7 +131,6 @@ export default {
                     encode: true,
                   }),
                   postcssFocus(),
-                  postcssNormalizeCharset(),
                 ],
               },
             },